Add a `note: ` prefix to all notes. (#4330)

Omit the `note: ` prefix and the snippet from the "in import" note that
precedes a diagnostic.

This makes our diagnostic output more closely match that of Clang and
GCC.

toolchain/check/sem_ir_diagnostic_converter.cpp

@@ -47,7 +47,8 @@ auto SemIRDiagnosticConverter::ConvertLoc(SemIRLoc loc,
     // TODO: Add an "In implicit import of prelude." note for the case where we
     // don't have a location.
     if (import_loc_id.is_valid()) {
-      CARBON_DIAGNOSTIC(InImport, Note, "in import");
+      // TODO: Include the name of the imported library in the diagnostic.
+      CARBON_DIAGNOSTIC(InImport, LocationInfo, "in import");
       context_fn(in_import_loc, InImport);
     }
 

toolchain/check/testdata/alias/no_prelude/fail_modifiers.carbon

@@ -17,21 +17,21 @@ class Class {}
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+21]]:10: error: `base` not allowed on declaration with `abstract`
 // CHECK:STDERR: abstract base default final alias A = Class;
 // CHECK:STDERR:          ^~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+18]]:1: `abstract` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+18]]:1: note: `abstract` previously appeared here
 // CHECK:STDERR: abstract base default final alias A = Class;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+14]]:15: error: `default` not allowed on declaration with `abstract`
 // CHECK:STDERR: abstract base default final alias A = Class;
 // CHECK:STDERR:               ^~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+11]]:1: `abstract` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+11]]:1: note: `abstract` previously appeared here
 // CHECK:STDERR: abstract base default final alias A = Class;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:23: error: `final` not allowed on declaration with `abstract`
 // CHECK:STDERR: abstract base default final alias A = Class;
 // CHECK:STDERR:                       ^~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `abstract` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `abstract` previously appeared here
 // CHECK:STDERR: abstract base default final alias A = Class;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:

toolchain/check/testdata/alias/no_prelude/fail_name_conflict.carbon

@@ -14,7 +14,7 @@ alias a = C;
 // CHECK:STDERR: fail_name_conflict.carbon:[[@LINE+7]]:5: error: duplicate name being declared in the same scope
 // CHECK:STDERR: var a: C = {};
 // CHECK:STDERR:     ^
-// CHECK:STDERR: fail_name_conflict.carbon:[[@LINE-4]]:7: name is previously declared here
+// CHECK:STDERR: fail_name_conflict.carbon:[[@LINE-4]]:7: note: name is previously declared here
 // CHECK:STDERR: alias a = C;
 // CHECK:STDERR:       ^
 // CHECK:STDERR:
@@ -24,7 +24,7 @@ var b: C = {};
 // CHECK:STDERR: fail_name_conflict.carbon:[[@LINE+6]]:7: error: duplicate name being declared in the same scope
 // CHECK:STDERR: alias b = C;
 // CHECK:STDERR:       ^
-// CHECK:STDERR: fail_name_conflict.carbon:[[@LINE-4]]:5: name is previously declared here
+// CHECK:STDERR: fail_name_conflict.carbon:[[@LINE-4]]:5: note: name is previously declared here
 // CHECK:STDERR: var b: C = {};
 // CHECK:STDERR:     ^
 alias b = C;

toolchain/check/testdata/alias/no_prelude/import.carbon

@@ -58,9 +58,7 @@ var b: () = a_alias;
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_var3.carbon:[[@LINE+6]]:1: in import
-// CHECK:STDERR: import library "var2";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_var3.carbon:[[@LINE+4]]:1: in import
 // CHECK:STDERR: var2.carbon:8:5: error: semantics TODO: `Non-constant ImportRefLoaded (comes up with var)`
 // CHECK:STDERR: var b: () = a_alias;
 // CHECK:STDERR:     ^
@@ -255,8 +253,8 @@ var c: () = a_alias_alias;
 // CHECK:STDOUT:     .c = %c
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %default.import = import <invalid>
-// CHECK:STDOUT:   %.loc12_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc12_9.2: type = converted %.loc12_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc10_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc10_9.2: type = converted %.loc10_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %c.var: ref %.1 = var c
 // CHECK:STDOUT:   %c: ref %.1 = bind_name c, %c.var
 // CHECK:STDOUT: }
@@ -264,9 +262,9 @@ var c: () = a_alias_alias;
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %a_alias_alias.ref: ref %.1 = name_ref a_alias_alias, imports.%import_ref.1 [template = <error>]
-// CHECK:STDOUT:   %.loc12_13: init %.1 = tuple_init () to file.%c.var [template = constants.%tuple]
-// CHECK:STDOUT:   %.loc12_26: init %.1 = converted %a_alias_alias.ref, %.loc12_13 [template = constants.%tuple]
-// CHECK:STDOUT:   assign file.%c.var, %.loc12_26
+// CHECK:STDOUT:   %.loc10_13: init %.1 = tuple_init () to file.%c.var [template = constants.%tuple]
+// CHECK:STDOUT:   %.loc10_26: init %.1 = converted %a_alias_alias.ref, %.loc10_13 [template = constants.%tuple]
+// CHECK:STDOUT:   assign file.%c.var, %.loc10_26
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/array/fail_bound_overflow.carbon

@@ -20,7 +20,7 @@ var a: [i32; 39999999999999999993];
 // CHECK:STDERR: fail_bound_overflow.carbon:[[@LINE+10]]:9: error: cannot implicitly convert from `i32` to `type`
 // CHECK:STDERR: var b: [1; 39999999999999999993];
 // CHECK:STDERR:         ^
-// CHECK:STDERR: fail_bound_overflow.carbon:[[@LINE+7]]:9: type `i32` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_bound_overflow.carbon:[[@LINE+7]]:9: note: type `i32` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var b: [1; 39999999999999999993];
 // CHECK:STDERR:         ^
 // CHECK:STDERR:

toolchain/check/testdata/array/fail_incomplete_element.carbon

@@ -13,7 +13,7 @@ class Incomplete;
 // CHECK:STDERR: fail_incomplete_element.carbon:[[@LINE+6]]:8: error: Variable has incomplete type `[Incomplete; 1]`
 // CHECK:STDERR: var a: [Incomplete; 1];
 // CHECK:STDERR:        ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_incomplete_element.carbon:[[@LINE-5]]:1: class was forward declared here
+// CHECK:STDERR: fail_incomplete_element.carbon:[[@LINE-5]]:1: note: class was forward declared here
 // CHECK:STDERR: class Incomplete;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
 var a: [Incomplete; 1];

toolchain/check/testdata/array/fail_invalid_type.carbon

@@ -11,7 +11,7 @@
 // CHECK:STDERR: fail_invalid_type.carbon:[[@LINE+6]]:9: error: cannot implicitly convert from `i32` to `type`
 // CHECK:STDERR: var a: [1; 1];
 // CHECK:STDERR:         ^
-// CHECK:STDERR: fail_invalid_type.carbon:[[@LINE+3]]:9: type `i32` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_invalid_type.carbon:[[@LINE+3]]:9: note: type `i32` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var a: [1; 1];
 // CHECK:STDERR:         ^
 var a: [1; 1];

toolchain/check/testdata/array/fail_type_mismatch.carbon

@@ -11,7 +11,7 @@
 // CHECK:STDERR: fail_type_mismatch.carbon:[[@LINE+7]]:19: error: cannot implicitly convert from `String` to `i32`
 // CHECK:STDERR: var a: [i32; 3] = (1, "Hello", "World");
 // CHECK:STDERR:                   ^~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_type_mismatch.carbon:[[@LINE+4]]:19: type `String` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_type_mismatch.carbon:[[@LINE+4]]:19: note: type `String` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var a: [i32; 3] = (1, "Hello", "World");
 // CHECK:STDERR:                   ^~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -21,7 +21,7 @@ var t1: (i32, String, String);
 // CHECK:STDERR: fail_type_mismatch.carbon:[[@LINE+7]]:19: error: cannot implicitly convert from `String` to `i32`
 // CHECK:STDERR: var b: [i32; 3] = t1;
 // CHECK:STDERR:                   ^~
-// CHECK:STDERR: fail_type_mismatch.carbon:[[@LINE+4]]:19: type `String` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_type_mismatch.carbon:[[@LINE+4]]:19: note: type `String` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var b: [i32; 3] = t1;
 // CHECK:STDERR:                   ^~
 // CHECK:STDERR:

toolchain/check/testdata/as/adapter_conversion.carbon

@@ -100,7 +100,7 @@ class B {
 // CHECK:STDERR: fail_adapt_init_from_struct.carbon:[[@LINE+6]]:12: error: cannot convert from `{.x: i32}` to `B` with `as`
 // CHECK:STDERR: var b: B = {.x = 1} as B;
 // CHECK:STDERR:            ^~~~~~~~~~~~~
-// CHECK:STDERR: fail_adapt_init_from_struct.carbon:[[@LINE+3]]:12: type `{.x: i32}` does not implement interface `As`
+// CHECK:STDERR: fail_adapt_init_from_struct.carbon:[[@LINE+3]]:12: note: type `{.x: i32}` does not implement interface `As`
 // CHECK:STDERR: var b: B = {.x = 1} as B;
 // CHECK:STDERR:            ^~~~~~~~~~~~~
 var b: B = {.x = 1} as B;

toolchain/check/testdata/as/fail_no_conversion.carbon

@@ -11,7 +11,7 @@
 // CHECK:STDERR: fail_no_conversion.carbon:[[@LINE+6]]:21: error: cannot convert from `i32` to `(i32, i32)` with `as`
 // CHECK:STDERR: let n: (i32, i32) = 1 as (i32, i32);
 // CHECK:STDERR:                     ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_no_conversion.carbon:[[@LINE+3]]:21: type `i32` does not implement interface `As`
+// CHECK:STDERR: fail_no_conversion.carbon:[[@LINE+3]]:21: note: type `i32` does not implement interface `As`
 // CHECK:STDERR: let n: (i32, i32) = 1 as (i32, i32);
 // CHECK:STDERR:                     ^~~~~~~~~~~~~~~
 let n: (i32, i32) = 1 as (i32, i32);

toolchain/check/testdata/as/fail_not_type.carbon

@@ -11,7 +11,7 @@
 // CHECK:STDERR: fail_not_type.carbon:[[@LINE+6]]:19: error: cannot implicitly convert from `i32` to `type`
 // CHECK:STDERR: let n: i32 = 1 as 2;
 // CHECK:STDERR:                   ^
-// CHECK:STDERR: fail_not_type.carbon:[[@LINE+3]]:19: type `i32` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_not_type.carbon:[[@LINE+3]]:19: note: type `i32` does not implement interface `ImplicitAs`
 // CHECK:STDERR: let n: i32 = 1 as 2;
 // CHECK:STDERR:                   ^
 let n: i32 = 1 as 2;

toolchain/check/testdata/basics/fail_non_type_as_type.carbon

@@ -11,7 +11,7 @@
 // CHECK:STDERR: fail_non_type_as_type.carbon:[[@LINE+6]]:1: error: cannot implicitly convert from `i32` to `type`
 // CHECK:STDERR: var x: type = 42;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_non_type_as_type.carbon:[[@LINE+3]]:1: type `i32` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_non_type_as_type.carbon:[[@LINE+3]]:1: note: type `i32` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var x: type = 42;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
 var x: type = 42;

toolchain/check/testdata/builtins/float/negate.carbon

@@ -43,7 +43,7 @@ fn RuntimeCallTooFew(a: f64) -> f64 {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:10: error: 1 argument(s) passed to function expecting 0 argument(s).
   // CHECK:STDERR:   return TooFew(a);
   // CHECK:STDERR:          ^~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-17]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-17]]:1: note: calling function declared here
   // CHECK:STDERR: fn TooFew() -> f64 = "float.negate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -54,7 +54,7 @@ fn RuntimeCallTooMany(a: f64, b: f64, c: f64) -> f64 {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:10: error: 3 argument(s) passed to function expecting 2 argument(s).
   // CHECK:STDERR:   return TooMany(a, b, c);
   // CHECK:STDERR:          ^~~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-23]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-23]]:1: note: calling function declared here
   // CHECK:STDERR: fn TooMany(a: f64, b: f64) -> f64 = "float.negate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -65,7 +65,7 @@ fn RuntimeCallBadReturnType(a: f64, b: f64) -> bool {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+6]]:10: error: 2 argument(s) passed to function expecting 1 argument(s).
   // CHECK:STDERR:   return BadReturnType(a, b);
   // CHECK:STDERR:          ^~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-29]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-29]]:1: note: calling function declared here
   // CHECK:STDERR: fn BadReturnType(a: f64) -> bool = "float.negate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   return BadReturnType(a, b);

toolchain/check/testdata/builtins/int/sadd.carbon

@@ -59,7 +59,7 @@ var bad_return_type: [i32; BadReturnType(1, 2)];
 // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:21: error: 3 argument(s) passed to function expecting 2 argument(s).
 // CHECK:STDERR: var bad_call: [i32; JustRight(1, 2, 3)];
 // CHECK:STDERR:                     ^~~~~~~~~~
-// CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-21]]:1: calling function declared here
+// CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-21]]:1: note: calling function declared here
 // CHECK:STDERR: fn JustRight(a: i32, b: i32) -> i32 = "int.sadd";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:

toolchain/check/testdata/builtins/int/snegate.carbon

@@ -61,7 +61,7 @@ var bad_return_type: [i32; BadReturnType(1)];
 // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:21: error: 2 argument(s) passed to function expecting 1 argument(s).
 // CHECK:STDERR: var bad_call: [i32; JustRight(1, 2)];
 // CHECK:STDERR:                     ^~~~~~~~~~
-// CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-21]]:1: calling function declared here
+// CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-21]]:1: note: calling function declared here
 // CHECK:STDERR: fn JustRight(a: i32) -> i32 = "int.snegate";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -71,7 +71,7 @@ fn RuntimeCallTooFew(a: i32) -> i32 {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:10: error: 1 argument(s) passed to function expecting 0 argument(s).
   // CHECK:STDERR:   return TooFew(a);
   // CHECK:STDERR:          ^~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-42]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-42]]:1: note: calling function declared here
   // CHECK:STDERR: fn TooFew() -> i32 = "int.snegate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -82,7 +82,7 @@ fn RuntimeCallTooMany(a: i32, b: i32, c: i32) -> i32 {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:10: error: 3 argument(s) passed to function expecting 2 argument(s).
   // CHECK:STDERR:   return TooMany(a, b, c);
   // CHECK:STDERR:          ^~~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-48]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-48]]:1: note: calling function declared here
   // CHECK:STDERR: fn TooMany(a: i32, b: i32) -> i32 = "int.snegate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -93,7 +93,7 @@ fn RuntimeCallBadReturnType(a: i32, b: i32) -> bool {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:10: error: 2 argument(s) passed to function expecting 1 argument(s).
   // CHECK:STDERR:   return BadReturnType(a, b);
   // CHECK:STDERR:          ^~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-54]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-54]]:1: note: calling function declared here
   // CHECK:STDERR: fn BadReturnType(a: i32) -> bool = "int.snegate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:

toolchain/check/testdata/builtins/int/uadd.carbon

@@ -59,7 +59,7 @@ var bad_return_type: [i32; BadReturnType(1, 2)];
 // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+6]]:21: error: 3 argument(s) passed to function expecting 2 argument(s).
 // CHECK:STDERR: var bad_call: [i32; JustRight(1, 2, 3)];
 // CHECK:STDERR:                     ^~~~~~~~~~
-// CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-21]]:1: calling function declared here
+// CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-21]]:1: note: calling function declared here
 // CHECK:STDERR: fn JustRight(a: i32, b: i32) -> i32 = "int.uadd";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 var bad_call: [i32; JustRight(1, 2, 3)];

toolchain/check/testdata/builtins/int/unegate.carbon

@@ -61,7 +61,7 @@ var bad_return_type: [i32; BadReturnType(1)];
 // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:21: error: 2 argument(s) passed to function expecting 1 argument(s).
 // CHECK:STDERR: var bad_call: [i32; JustRight(1, 2)];
 // CHECK:STDERR:                     ^~~~~~~~~~
-// CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-21]]:1: calling function declared here
+// CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-21]]:1: note: calling function declared here
 // CHECK:STDERR: fn JustRight(a: i32) -> i32 = "int.unegate";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -71,7 +71,7 @@ fn RuntimeCallTooFew(a: i32) -> i32 {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:10: error: 1 argument(s) passed to function expecting 0 argument(s).
   // CHECK:STDERR:   return TooFew(a);
   // CHECK:STDERR:          ^~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-42]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-42]]:1: note: calling function declared here
   // CHECK:STDERR: fn TooFew() -> i32 = "int.unegate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -82,7 +82,7 @@ fn RuntimeCallTooMany(a: i32, b: i32, c: i32) -> i32 {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+7]]:10: error: 3 argument(s) passed to function expecting 2 argument(s).
   // CHECK:STDERR:   return TooMany(a, b, c);
   // CHECK:STDERR:          ^~~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-48]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-48]]:1: note: calling function declared here
   // CHECK:STDERR: fn TooMany(a: i32, b: i32) -> i32 = "int.unegate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -93,7 +93,7 @@ fn RuntimeCallBadReturnType(a: i32, b: i32) -> bool {
   // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE+6]]:10: error: 2 argument(s) passed to function expecting 1 argument(s).
   // CHECK:STDERR:   return BadReturnType(a, b);
   // CHECK:STDERR:          ^~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-54]]:1: calling function declared here
+  // CHECK:STDERR: fail_bad_decl.carbon:[[@LINE-54]]:1: note: calling function declared here
   // CHECK:STDERR: fn BadReturnType(a: i32) -> bool = "int.unegate";
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   return BadReturnType(a, b);

toolchain/check/testdata/class/access_modifers.carbon

@@ -30,7 +30,7 @@ fn Run() {
   // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE+7]]:21: error: cannot access private member `radius` of type `Circle`
   // CHECK:STDERR:   let radius: i32 = circle.radius;
   // CHECK:STDERR:                     ^~~~~~~~~~~~~
-  // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE-17]]:15: the private member `radius` is defined here
+  // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE-17]]:15: note: the private member `radius` is defined here
   // CHECK:STDERR:   private var radius: i32;
   // CHECK:STDERR:               ^~~~~~~~~~~
   // CHECK:STDERR:
@@ -38,7 +38,7 @@ fn Run() {
   // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE+7]]:3: error: cannot access private member `radius` of type `Circle`
   // CHECK:STDERR:   circle.radius = 5;
   // CHECK:STDERR:   ^~~~~~~~~~~~~
-  // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE-25]]:15: the private member `radius` is defined here
+  // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE-25]]:15: note: the private member `radius` is defined here
   // CHECK:STDERR:   private var radius: i32;
   // CHECK:STDERR:               ^~~~~~~~~~~
   // CHECK:STDERR:
@@ -46,7 +46,7 @@ fn Run() {
   // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE+7]]:3: error: cannot access private member `SOME_INTERNAL_CONSTANT` of type `Circle`
   // CHECK:STDERR:   circle.SOME_INTERNAL_CONSTANT;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE-32]]:15: the private member `SOME_INTERNAL_CONSTANT` is defined here
+  // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE-32]]:15: note: the private member `SOME_INTERNAL_CONSTANT` is defined here
   // CHECK:STDERR:   private let SOME_INTERNAL_CONSTANT: i32 = 5;
   // CHECK:STDERR:               ^~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -55,7 +55,7 @@ fn Run() {
   // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE+7]]:3: error: cannot access private member `SomeInternalFunction` of type `Circle`
   // CHECK:STDERR:   circle.SomeInternalFunction();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE-39]]:3: the private member `SomeInternalFunction` is defined here
+  // CHECK:STDERR: fail_private_field_access.carbon:[[@LINE-39]]:3: note: the private member `SomeInternalFunction` is defined here
   // CHECK:STDERR:   private fn SomeInternalFunction() -> i32 {
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -74,7 +74,7 @@ fn Run() {
   // CHECK:STDERR: fail_protected_field_access.carbon:[[@LINE+7]]:16: error: cannot access protected member `x` of type `A`
   // CHECK:STDERR:   let x: i32 = A.x;
   // CHECK:STDERR:                ^~~
-  // CHECK:STDERR: fail_protected_field_access.carbon:[[@LINE-7]]:17: the protected member `x` is defined here
+  // CHECK:STDERR: fail_protected_field_access.carbon:[[@LINE-7]]:17: note: the protected member `x` is defined here
   // CHECK:STDERR:   protected var x: i32;
   // CHECK:STDERR:                 ^~~~~~
   // CHECK:STDERR:
@@ -123,7 +123,7 @@ class A {
 // CHECK:STDERR: fail_global_access.carbon:[[@LINE+7]]:14: error: cannot access protected member `x` of type `A`
 // CHECK:STDERR: let x: i32 = A.x;
 // CHECK:STDERR:              ^~~
-// CHECK:STDERR: fail_global_access.carbon:[[@LINE-7]]:17: the protected member `x` is defined here
+// CHECK:STDERR: fail_global_access.carbon:[[@LINE-7]]:17: note: the protected member `x` is defined here
 // CHECK:STDERR:   protected let x: i32 = 5;
 // CHECK:STDERR:                 ^
 // CHECK:STDERR:
@@ -131,7 +131,7 @@ let x: i32 = A.x;
 // CHECK:STDERR: fail_global_access.carbon:[[@LINE+6]]:14: error: cannot access private member `y` of type `A`
 // CHECK:STDERR: let y: i32 = A.y;
 // CHECK:STDERR:              ^~~
-// CHECK:STDERR: fail_global_access.carbon:[[@LINE-14]]:15: the private member `y` is defined here
+// CHECK:STDERR: fail_global_access.carbon:[[@LINE-14]]:15: note: the private member `y` is defined here
 // CHECK:STDERR:   private let y: i32 = 5;
 // CHECK:STDERR:               ^
 let y: i32 = A.y;

toolchain/check/testdata/class/cross_package_import.carbon

@@ -48,13 +48,11 @@ library "[[@TEST_NAME]]";
 
 import Other library "other_extern";
 
-// CHECK:STDERR: fail_extern.carbon:[[@LINE+10]]:8: error: Variable has incomplete type `C`
+// CHECK:STDERR: fail_extern.carbon:[[@LINE+8]]:8: error: Variable has incomplete type `C`
 // CHECK:STDERR: var c: Other.C = {};
 // CHECK:STDERR:        ^~~~~~~
 // CHECK:STDERR: fail_extern.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import Other library "other_extern";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: other_extern.carbon:4:1: class was forward declared here
+// CHECK:STDERR: other_extern.carbon:4:1: note: class was forward declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -64,22 +62,18 @@ var c: Other.C = {};
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_todo_merge_define_extern.carbon:[[@LINE+12]]:1: in import
-// CHECK:STDERR: import Other library "other_define";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_todo_merge_define_extern.carbon:[[@LINE+8]]:1: in import
 // CHECK:STDERR: other_extern.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_todo_merge_define_extern.carbon:[[@LINE+6]]:1: in import
-// CHECK:STDERR: import Other library "other_define";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: other_define.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_todo_merge_define_extern.carbon:[[@LINE+4]]:1: in import
+// CHECK:STDERR: other_define.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
 import Other library "other_define";
 import Other library "other_extern";
 
-// CHECK:STDERR: fail_todo_merge_define_extern.carbon:[[@LINE+4]]:8: in name lookup for `C`
+// CHECK:STDERR: fail_todo_merge_define_extern.carbon:[[@LINE+4]]:8: note: in name lookup for `C`
 // CHECK:STDERR: var c: Other.C = {};
 // CHECK:STDERR:        ^~~~~~~
 // CHECK:STDERR:
@@ -89,22 +83,18 @@ var c: Other.C = {};
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_conflict.carbon:[[@LINE+12]]:1: in import
-// CHECK:STDERR: import Other library "other_define";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_conflict.carbon:[[@LINE+8]]:1: in import
 // CHECK:STDERR: other_conflict.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn C() {}
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_conflict.carbon:[[@LINE+6]]:1: in import
-// CHECK:STDERR: import Other library "other_define";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: other_define.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_conflict.carbon:[[@LINE+4]]:1: in import
+// CHECK:STDERR: other_define.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
 import Other library "other_define";
 import Other library "other_conflict";
 
-// CHECK:STDERR: fail_conflict.carbon:[[@LINE+3]]:8: in name lookup for `C`
+// CHECK:STDERR: fail_conflict.carbon:[[@LINE+3]]:8: note: in name lookup for `C`
 // CHECK:STDERR: var c: Other.C = {};
 // CHECK:STDERR:        ^~~~~~~
 var c: Other.C = {};
@@ -312,7 +302,7 @@ var c: Other.C = {};
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
-// CHECK:STDOUT:   %.loc16: %.1 = struct_literal ()
+// CHECK:STDOUT:   %.loc14: %.1 = struct_literal ()
 // CHECK:STDOUT:   assign file.%c.var, <error>
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
@@ -370,10 +360,10 @@ var c: Other.C = {};
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
-// CHECK:STDOUT:   %.loc23_19.1: %.1 = struct_literal ()
-// CHECK:STDOUT:   %.loc23_19.2: init %C = class_init (), file.%c.var [template = constants.%struct]
-// CHECK:STDOUT:   %.loc23_20: init %C = converted %.loc23_19.1, %.loc23_19.2 [template = constants.%struct]
-// CHECK:STDOUT:   assign file.%c.var, %.loc23_20
+// CHECK:STDOUT:   %.loc19_19.1: %.1 = struct_literal ()
+// CHECK:STDOUT:   %.loc19_19.2: init %C = class_init (), file.%c.var [template = constants.%struct]
+// CHECK:STDOUT:   %.loc19_20: init %C = converted %.loc19_19.1, %.loc19_19.2 [template = constants.%struct]
+// CHECK:STDOUT:   assign file.%c.var, %.loc19_20
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -430,10 +420,10 @@ var c: Other.C = {};
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
-// CHECK:STDOUT:   %.loc22_19.1: %.1 = struct_literal ()
-// CHECK:STDOUT:   %.loc22_19.2: init %C = class_init (), file.%c.var [template = constants.%struct]
-// CHECK:STDOUT:   %.loc22_20: init %C = converted %.loc22_19.1, %.loc22_19.2 [template = constants.%struct]
-// CHECK:STDOUT:   assign file.%c.var, %.loc22_20
+// CHECK:STDOUT:   %.loc18_19.1: %.1 = struct_literal ()
+// CHECK:STDOUT:   %.loc18_19.2: init %C = class_init (), file.%c.var [template = constants.%struct]
+// CHECK:STDOUT:   %.loc18_20: init %C = converted %.loc18_19.1, %.loc18_19.2 [template = constants.%struct]
+// CHECK:STDOUT:   assign file.%c.var, %.loc18_20
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/class/extend_adapt.carbon

@@ -51,10 +51,10 @@ fn F(a: SomeClassAdapter) {
   // CHECK:STDERR: fail_todo_method_access.carbon:[[@LINE+10]]:3: error: cannot implicitly convert from `SomeClassAdapter` to `SomeClass`
   // CHECK:STDERR:   a.F();
   // CHECK:STDERR:   ^~~~
-  // CHECK:STDERR: fail_todo_method_access.carbon:[[@LINE+7]]:3: type `SomeClassAdapter` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_todo_method_access.carbon:[[@LINE+7]]:3: note: type `SomeClassAdapter` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   a.F();
   // CHECK:STDERR:   ^~~~
-  // CHECK:STDERR: fail_todo_method_access.carbon:[[@LINE-14]]:8: initializing `self` parameter of method declared here
+  // CHECK:STDERR: fail_todo_method_access.carbon:[[@LINE-14]]:8: note: initializing `self` parameter of method declared here
   // CHECK:STDERR:   fn F[self: Self]();
   // CHECK:STDERR:        ^~~~
   // CHECK:STDERR:
@@ -78,7 +78,7 @@ fn F(a: SomeClassAdapter) -> i32 {
   // CHECK:STDERR: fail_todo_field_access.carbon:[[@LINE+7]]:10: error: cannot implicitly convert from `SomeClassAdapter` to `SomeClass`
   // CHECK:STDERR:   return a.b;
   // CHECK:STDERR:          ^~~
-  // CHECK:STDERR: fail_todo_field_access.carbon:[[@LINE+4]]:10: type `SomeClassAdapter` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_todo_field_access.carbon:[[@LINE+4]]:10: note: type `SomeClassAdapter` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   return a.b;
   // CHECK:STDERR:          ^~~
   // CHECK:STDERR:

toolchain/check/testdata/class/fail_adapt_bad_decl.carbon

@@ -16,7 +16,7 @@ class Bad {
   // CHECK:STDERR: fail_not_type.carbon:[[@LINE+7]]:3: error: cannot implicitly convert from `i32` to `type`
   // CHECK:STDERR:   adapt 100;
   // CHECK:STDERR:   ^~~~~~~~~~
-  // CHECK:STDERR: fail_not_type.carbon:[[@LINE+4]]:3: type `i32` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_not_type.carbon:[[@LINE+4]]:3: note: type `i32` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   adapt 100;
   // CHECK:STDERR:   ^~~~~~~~~~
   // CHECK:STDERR:
@@ -37,7 +37,7 @@ class Bad {
   // CHECK:STDERR: fail_extend_not_type.carbon:[[@LINE+7]]:3: error: cannot implicitly convert from `i32` to `type`
   // CHECK:STDERR:   extend adapt 100;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_extend_not_type.carbon:[[@LINE+4]]:3: type `i32` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_extend_not_type.carbon:[[@LINE+4]]:3: note: type `i32` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   extend adapt 100;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -56,7 +56,7 @@ class MultipleAdapts {
   // CHECK:STDERR: fail_repeated.carbon:[[@LINE+7]]:3: error: multiple `adapt` declarations in class
   // CHECK:STDERR:   adapt {};
   // CHECK:STDERR:   ^~~~~~~~~
-  // CHECK:STDERR: fail_repeated.carbon:[[@LINE-4]]:3: previous `adapt` declaration is here
+  // CHECK:STDERR: fail_repeated.carbon:[[@LINE-4]]:3: note: previous `adapt` declaration is here
   // CHECK:STDERR:   adapt ();
   // CHECK:STDERR:   ^~~~~~~~~
   // CHECK:STDERR:
@@ -68,7 +68,7 @@ class MultipleAdaptsSameType {
   // CHECK:STDERR: fail_repeated.carbon:[[@LINE+7]]:3: error: multiple `adapt` declarations in class
   // CHECK:STDERR:   adapt ();
   // CHECK:STDERR:   ^~~~~~~~~
-  // CHECK:STDERR: fail_repeated.carbon:[[@LINE-4]]:3: previous `adapt` declaration is here
+  // CHECK:STDERR: fail_repeated.carbon:[[@LINE-4]]:3: note: previous `adapt` declaration is here
   // CHECK:STDERR:   adapt ();
   // CHECK:STDERR:   ^~~~~~~~~
   // CHECK:STDERR:

toolchain/check/testdata/class/fail_adapt_bad_type.carbon

@@ -18,7 +18,7 @@ class AdaptIncomplete {
   // CHECK:STDERR: fail_incomplete_type.carbon:[[@LINE+6]]:3: error: adapted type `Incomplete` is an incomplete type
   // CHECK:STDERR:   adapt Incomplete;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete_type.carbon:[[@LINE-6]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete_type.carbon:[[@LINE-6]]:1: note: class was forward declared here
   // CHECK:STDERR: class Incomplete;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
   adapt Incomplete;

toolchain/check/testdata/class/fail_adapt_modifiers.carbon

@@ -38,7 +38,7 @@ class C4 {
   // CHECK:STDERR: fail_adapt_modifiers.carbon:[[@LINE+7]]:10: error: `extend` repeated on declaration
   // CHECK:STDERR:   extend extend adapt B;
   // CHECK:STDERR:          ^~~~~~
-  // CHECK:STDERR: fail_adapt_modifiers.carbon:[[@LINE+4]]:3: `extend` previously appeared here
+  // CHECK:STDERR: fail_adapt_modifiers.carbon:[[@LINE+4]]:3: note: `extend` previously appeared here
   // CHECK:STDERR:   extend extend adapt B;
   // CHECK:STDERR:   ^~~~~~
   // CHECK:STDERR:
@@ -49,7 +49,7 @@ class C5 {
   // CHECK:STDERR: fail_adapt_modifiers.carbon:[[@LINE+6]]:10: error: `base` not allowed on declaration with `extend`
   // CHECK:STDERR:   extend base adapt B;
   // CHECK:STDERR:          ^~~~
-  // CHECK:STDERR: fail_adapt_modifiers.carbon:[[@LINE+3]]:3: `extend` previously appeared here
+  // CHECK:STDERR: fail_adapt_modifiers.carbon:[[@LINE+3]]:3: note: `extend` previously appeared here
   // CHECK:STDERR:   extend base adapt B;
   // CHECK:STDERR:   ^~~~~~
   extend base adapt B;

toolchain/check/testdata/class/fail_adapt_with_subobjects.carbon

@@ -19,7 +19,7 @@ class AdaptWithBase {
   // CHECK:STDERR:   adapt i32;
   // CHECK:STDERR:   ^~~~~~~~~~
   adapt i32;
-  // CHECK:STDERR: fail_adapt_with_base.carbon:[[@LINE+4]]:3: `base` declaration is here
+  // CHECK:STDERR: fail_adapt_with_base.carbon:[[@LINE+4]]:3: note: `base` declaration is here
   // CHECK:STDERR:   extend base: Base;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -35,7 +35,7 @@ class AdaptWithField {
   // CHECK:STDERR:   adapt i32;
   // CHECK:STDERR:   ^~~~~~~~~~
   adapt i32;
-  // CHECK:STDERR: fail_adapt_with_fields.carbon:[[@LINE+4]]:7: first field declaration is here
+  // CHECK:STDERR: fail_adapt_with_fields.carbon:[[@LINE+4]]:7: note: first field declaration is here
   // CHECK:STDERR:   var n: i32;
   // CHECK:STDERR:       ^~~~~~
   // CHECK:STDERR:
@@ -47,7 +47,7 @@ class AdaptWithFields {
   // CHECK:STDERR:   adapt i32;
   // CHECK:STDERR:   ^~~~~~~~~~
   adapt i32;
-  // CHECK:STDERR: fail_adapt_with_fields.carbon:[[@LINE+4]]:7: first field declaration is here
+  // CHECK:STDERR: fail_adapt_with_fields.carbon:[[@LINE+4]]:7: note: first field declaration is here
   // CHECK:STDERR:   var a: i32;
   // CHECK:STDERR:       ^~~~~~
   // CHECK:STDERR:
@@ -68,7 +68,7 @@ class AdaptWithBaseAndFields {
   // CHECK:STDERR: fail_adapt_with_base_and_fields.carbon:[[@LINE+6]]:3: error: adapter with base class
   // CHECK:STDERR:   adapt {};
   // CHECK:STDERR:   ^~~~~~~~~
-  // CHECK:STDERR: fail_adapt_with_base_and_fields.carbon:[[@LINE-5]]:3: `base` declaration is here
+  // CHECK:STDERR: fail_adapt_with_base_and_fields.carbon:[[@LINE-5]]:3: note: `base` declaration is here
   // CHECK:STDERR:   extend base: Base;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~
   adapt {};

toolchain/check/testdata/class/fail_addr_self.carbon

@@ -17,7 +17,7 @@ fn F(c: Class, p: Class*) {
   // CHECK:STDERR: fail_addr_self.carbon:[[@LINE+7]]:6: error: `addr self` method cannot be invoked on a value
   // CHECK:STDERR:   c.F();
   // CHECK:STDERR:      ^
-  // CHECK:STDERR: fail_addr_self.carbon:[[@LINE-8]]:13: initializing `addr self` parameter of method declared here
+  // CHECK:STDERR: fail_addr_self.carbon:[[@LINE-8]]:13: note: initializing `addr self` parameter of method declared here
   // CHECK:STDERR:   fn F[addr self: Class*]();
   // CHECK:STDERR:             ^~~~
   // CHECK:STDERR:
@@ -26,7 +26,7 @@ fn F(c: Class, p: Class*) {
   // CHECK:STDERR: fail_addr_self.carbon:[[@LINE+7]]:6: error: `addr self` method cannot be invoked on a value
   // CHECK:STDERR:   c.G();
   // CHECK:STDERR:      ^
-  // CHECK:STDERR: fail_addr_self.carbon:[[@LINE-16]]:13: initializing `addr self` parameter of method declared here
+  // CHECK:STDERR: fail_addr_self.carbon:[[@LINE-16]]:13: note: initializing `addr self` parameter of method declared here
   // CHECK:STDERR:   fn G[addr self: Class]();
   // CHECK:STDERR:             ^~~~
   // CHECK:STDERR:
@@ -38,10 +38,10 @@ fn F(c: Class, p: Class*) {
   // CHECK:STDERR: fail_addr_self.carbon:[[@LINE+9]]:3: error: cannot implicitly convert from `Class*` to `Class`
   // CHECK:STDERR:   (*p).G();
   // CHECK:STDERR:   ^~~~~~~
-  // CHECK:STDERR: fail_addr_self.carbon:[[@LINE+6]]:3: type `Class*` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_addr_self.carbon:[[@LINE+6]]:3: note: type `Class*` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   (*p).G();
   // CHECK:STDERR:   ^~~~~~~
-  // CHECK:STDERR: fail_addr_self.carbon:[[@LINE-31]]:13: initializing `addr self` parameter of method declared here
+  // CHECK:STDERR: fail_addr_self.carbon:[[@LINE-31]]:13: note: initializing `addr self` parameter of method declared here
   // CHECK:STDERR:   fn G[addr self: Class]();
   // CHECK:STDERR:             ^~~~
   (*p).G();

toolchain/check/testdata/class/fail_base_bad_type.carbon

@@ -28,7 +28,7 @@ class DeriveFromNonType {
   // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+7]]:16: error: cannot implicitly convert from `i32` to `type`
   // CHECK:STDERR:   extend base: 32;
   // CHECK:STDERR:                ^~
-  // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:16: type `i32` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:16: note: type `i32` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   extend base: 32;
   // CHECK:STDERR:                ^~
   // CHECK:STDERR:
@@ -50,7 +50,7 @@ class DeriveFromi32 {
 // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+7]]:53: error: cannot implicitly convert from `DeriveFromi32*` to `i32*`
 // CHECK:STDERR: fn ConvertToBadBasei32(p: DeriveFromi32*) -> i32* { return p; }
 // CHECK:STDERR:                                                     ^~~~~~~~~
-// CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:53: type `DeriveFromi32*` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:53: note: type `DeriveFromi32*` does not implement interface `ImplicitAs`
 // CHECK:STDERR: fn ConvertToBadBasei32(p: DeriveFromi32*) -> i32* { return p; }
 // CHECK:STDERR:                                                     ^~~~~~~~~
 // CHECK:STDERR:
@@ -69,7 +69,7 @@ class DeriveFromTuple {
 // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+7]]:61: error: cannot implicitly convert from `DeriveFromTuple*` to `(Base,)*`
 // CHECK:STDERR: fn ConvertToBadBaseTuple(p: DeriveFromTuple*) -> (Base,)* { return p; }
 // CHECK:STDERR:                                                             ^~~~~~~~~
-// CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:61: type `DeriveFromTuple*` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:61: note: type `DeriveFromTuple*` does not implement interface `ImplicitAs`
 // CHECK:STDERR: fn ConvertToBadBaseTuple(p: DeriveFromTuple*) -> (Base,)* { return p; }
 // CHECK:STDERR:                                                             ^~~~~~~~~
 // CHECK:STDERR:
@@ -90,7 +90,7 @@ class DeriveFromStruct {
 // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+7]]:74: error: cannot implicitly convert from `DeriveFromStruct*` to `{.a: i32, .b: i32}*`
 // CHECK:STDERR: fn ConvertToBadBaseStruct(p: DeriveFromStruct*) -> {.a: i32, .b: i32}* { return p; }
 // CHECK:STDERR:                                                                          ^~~~~~~~~
-// CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:74: type `DeriveFromStruct*` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:74: note: type `DeriveFromStruct*` does not implement interface `ImplicitAs`
 // CHECK:STDERR: fn ConvertToBadBaseStruct(p: DeriveFromStruct*) -> {.a: i32, .b: i32}* { return p; }
 // CHECK:STDERR:                                                                          ^~~~~~~~~
 // CHECK:STDERR:
@@ -105,7 +105,7 @@ class DeriveFromIncomplete {
   // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+7]]:16: error: base `Incomplete` is an incomplete type
   // CHECK:STDERR:   extend base: Incomplete;
   // CHECK:STDERR:                ^~~~~~~~~~
-  // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE-6]]:1: class was forward declared here
+  // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE-6]]:1: note: class was forward declared here
   // CHECK:STDERR: base class Incomplete;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -115,7 +115,7 @@ class DeriveFromIncomplete {
 // CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+7]]:74: error: cannot implicitly convert from `DeriveFromIncomplete*` to `Incomplete*`
 // CHECK:STDERR: fn ConvertToBadBaseIncomplete(p: DeriveFromIncomplete*) -> Incomplete* { return p; }
 // CHECK:STDERR:                                                                          ^~~~~~~~~
-// CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:74: type `DeriveFromIncomplete*` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_base_bad_type.carbon:[[@LINE+4]]:74: note: type `DeriveFromIncomplete*` does not implement interface `ImplicitAs`
 // CHECK:STDERR: fn ConvertToBadBaseIncomplete(p: DeriveFromIncomplete*) -> Incomplete* { return p; }
 // CHECK:STDERR:                                                                          ^~~~~~~~~
 // CHECK:STDERR:

toolchain/check/testdata/class/fail_base_modifiers.carbon

@@ -34,7 +34,7 @@ class C3 {
   // CHECK:STDERR: fail_base_modifiers.carbon:[[@LINE+7]]:10: error: `default` not allowed on declaration with `extend`
   // CHECK:STDERR:   extend default base: B;
   // CHECK:STDERR:          ^~~~~~~
-  // CHECK:STDERR: fail_base_modifiers.carbon:[[@LINE+4]]:3: `extend` previously appeared here
+  // CHECK:STDERR: fail_base_modifiers.carbon:[[@LINE+4]]:3: note: `extend` previously appeared here
   // CHECK:STDERR:   extend default base: B;
   // CHECK:STDERR:   ^~~~~~
   // CHECK:STDERR:
@@ -45,7 +45,7 @@ class C4 {
   // CHECK:STDERR: fail_base_modifiers.carbon:[[@LINE+6]]:10: error: `extend` repeated on declaration
   // CHECK:STDERR:   extend extend base: B;
   // CHECK:STDERR:          ^~~~~~
-  // CHECK:STDERR: fail_base_modifiers.carbon:[[@LINE+3]]:3: `extend` previously appeared here
+  // CHECK:STDERR: fail_base_modifiers.carbon:[[@LINE+3]]:3: note: `extend` previously appeared here
   // CHECK:STDERR:   extend extend base: B;
   // CHECK:STDERR:   ^~~~~~
   extend extend base: B;

toolchain/check/testdata/class/fail_base_repeated.carbon

@@ -16,7 +16,7 @@ class C {
   // CHECK:STDERR: fail_base_repeated.carbon:[[@LINE+7]]:3: error: multiple `base` declarations in class; multiple inheritance is not permitted
   // CHECK:STDERR:   extend base: B2;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_base_repeated.carbon:[[@LINE-4]]:3: previous `base` declaration is here
+  // CHECK:STDERR: fail_base_repeated.carbon:[[@LINE-4]]:3: note: previous `base` declaration is here
   // CHECK:STDERR:   extend base: B1;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -29,7 +29,7 @@ class D {
   // CHECK:STDERR: fail_base_repeated.carbon:[[@LINE+6]]:3: error: multiple `base` declarations in class; multiple inheritance is not permitted
   // CHECK:STDERR:   extend base: B1;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_base_repeated.carbon:[[@LINE-4]]:3: previous `base` declaration is here
+  // CHECK:STDERR: fail_base_repeated.carbon:[[@LINE-4]]:3: note: previous `base` declaration is here
   // CHECK:STDERR:   extend base: B1;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~
   extend base: B1;

toolchain/check/testdata/class/fail_compound_type_mismatch.carbon

@@ -20,7 +20,7 @@ fn AccessBInA(a: A) -> i32 {
   // CHECK:STDERR: fail_compound_type_mismatch.carbon:[[@LINE+6]]:10: error: cannot implicitly convert from `A` to `B`
   // CHECK:STDERR:   return a.(B.b);
   // CHECK:STDERR:          ^~~~~~~
-  // CHECK:STDERR: fail_compound_type_mismatch.carbon:[[@LINE+3]]:10: type `A` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_compound_type_mismatch.carbon:[[@LINE+3]]:10: note: type `A` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   return a.(B.b);
   // CHECK:STDERR:          ^~~~~~~
   return a.(B.b);

toolchain/check/testdata/class/fail_derived_to_base.carbon

@@ -24,7 +24,7 @@ class B2 {
 // CHECK:STDERR: fail_derived_to_base.carbon:[[@LINE+7]]:38: error: cannot implicitly convert from `B2*` to `A1*`
 // CHECK:STDERR: fn ConvertUnrelated(p: B2*) -> A1* { return p; }
 // CHECK:STDERR:                                      ^~~~~~~~~
-// CHECK:STDERR: fail_derived_to_base.carbon:[[@LINE+4]]:38: type `B2*` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_derived_to_base.carbon:[[@LINE+4]]:38: note: type `B2*` does not implement interface `ImplicitAs`
 // CHECK:STDERR: fn ConvertUnrelated(p: B2*) -> A1* { return p; }
 // CHECK:STDERR:                                      ^~~~~~~~~
 // CHECK:STDERR:
@@ -35,7 +35,7 @@ class Incomplete;
 // CHECK:STDERR: fail_derived_to_base.carbon:[[@LINE+6]]:47: error: cannot implicitly convert from `Incomplete*` to `A2*`
 // CHECK:STDERR: fn ConvertIncomplete(p: Incomplete*) -> A2* { return p; }
 // CHECK:STDERR:                                               ^~~~~~~~~
-// CHECK:STDERR: fail_derived_to_base.carbon:[[@LINE+3]]:47: type `Incomplete*` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_derived_to_base.carbon:[[@LINE+3]]:47: note: type `Incomplete*` does not implement interface `ImplicitAs`
 // CHECK:STDERR: fn ConvertIncomplete(p: Incomplete*) -> A2* { return p; }
 // CHECK:STDERR:                                               ^~~~~~~~~
 fn ConvertIncomplete(p: Incomplete*) -> A2* { return p; }

toolchain/check/testdata/class/fail_extend_cycle.carbon

@@ -19,7 +19,7 @@ base class B {
 // CHECK:STDERR: fail_extend_cycle.carbon:[[@LINE+7]]:1: error: redefinition of `class A`
 // CHECK:STDERR: base class A {
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_extend_cycle.carbon:[[@LINE-11]]:1: previously defined here
+// CHECK:STDERR: fail_extend_cycle.carbon:[[@LINE-11]]:1: note: previously defined here
 // CHECK:STDERR: base class A {
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:

toolchain/check/testdata/class/fail_generic_method.carbon

@@ -18,7 +18,7 @@ class Class(T:! type) {
 // CHECK:STDERR: fail_generic_method.carbon:[[@LINE+14]]:10: error: redeclaration differs at parameter 1
 // CHECK:STDERR: fn Class(N:! i32).F[self: Self](n: T) {}
 // CHECK:STDERR:          ^
-// CHECK:STDERR: fail_generic_method.carbon:[[@LINE-10]]:13: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_generic_method.carbon:[[@LINE-10]]:13: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: class Class(T:! type) {
 // CHECK:STDERR:             ^
 // CHECK:STDERR:

toolchain/check/testdata/class/fail_import_misuses.carbon

@@ -23,26 +23,22 @@ library "[[@TEST_NAME]]";
 
 import library "a";
 
-// CHECK:STDERR: fail_b.carbon:[[@LINE+10]]:1: error: redeclaration of `class Empty` is redundant
+// CHECK:STDERR: fail_b.carbon:[[@LINE+8]]:1: error: redeclaration of `class Empty` is redundant
 // CHECK:STDERR: class Empty {
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR: fail_b.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "a";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: a.carbon:4:1: previously declared here
+// CHECK:STDERR: a.carbon:4:1: note: previously declared here
 // CHECK:STDERR: class Empty {
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR:
 class Empty {
 }
 
-// CHECK:STDERR: fail_b.carbon:[[@LINE+9]]:8: error: Variable has incomplete type `Incomplete`
+// CHECK:STDERR: fail_b.carbon:[[@LINE+7]]:8: error: Variable has incomplete type `Incomplete`
 // CHECK:STDERR: var a: Incomplete;
 // CHECK:STDERR:        ^~~~~~~~~~
-// CHECK:STDERR: fail_b.carbon:[[@LINE-18]]:1: in import
-// CHECK:STDERR: import library "a";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: a.carbon:7:1: class was forward declared here
+// CHECK:STDERR: fail_b.carbon:[[@LINE-16]]:1: in import
+// CHECK:STDERR: a.carbon:7:1: note: class was forward declared here
 // CHECK:STDERR: class Incomplete;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
 var a: Incomplete;
@@ -136,7 +132,7 @@ var a: Incomplete;
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @.1 {
-// CHECK:STDOUT:   %.loc17: <witness> = complete_type_witness %.1 [template = constants.%.2]
+// CHECK:STDOUT:   %.loc15: <witness> = complete_type_witness %.1 [template = constants.%.2]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = constants.%.3

toolchain/check/testdata/class/fail_incomplete.carbon

@@ -13,7 +13,7 @@ class Class;
 // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+7]]:4: error: cannot declare a member of incomplete class `Class`
 // CHECK:STDERR: fn Class.Function() {}
 // CHECK:STDERR:    ^~~~~
-// CHECK:STDERR: fail_incomplete.carbon:[[@LINE-5]]:1: class was forward declared here
+// CHECK:STDERR: fail_incomplete.carbon:[[@LINE-5]]:1: note: class was forward declared here
 // CHECK:STDERR: class Class;
 // CHECK:STDERR: ^~~~~~~~~~~~
 // CHECK:STDERR:
@@ -23,7 +23,7 @@ fn CallClassFunction() {
   // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+7]]:3: error: member access into incomplete class `Class`
   // CHECK:STDERR:   Class.Function();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-15]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-15]]:1: note: class was forward declared here
   // CHECK:STDERR: class Class;
   // CHECK:STDERR: ^~~~~~~~~~~~
   // CHECK:STDERR:
@@ -33,7 +33,7 @@ fn CallClassFunction() {
 // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+7]]:17: error: Variable has incomplete type `Class`
 // CHECK:STDERR: var global_var: Class;
 // CHECK:STDERR:                 ^~~~~
-// CHECK:STDERR: fail_incomplete.carbon:[[@LINE-25]]:1: class was forward declared here
+// CHECK:STDERR: fail_incomplete.carbon:[[@LINE-25]]:1: note: class was forward declared here
 // CHECK:STDERR: class Class;
 // CHECK:STDERR: ^~~~~~~~~~~~
 // CHECK:STDERR:
@@ -42,7 +42,7 @@ var global_var: Class;
 // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+7]]:24: error: function returns incomplete type `Class`
 // CHECK:STDERR: fn ConvertFromStruct() -> Class { return {}; }
 // CHECK:STDERR:                        ^~~~~~~~
-// CHECK:STDERR: fail_incomplete.carbon:[[@LINE-34]]:1: class was forward declared here
+// CHECK:STDERR: fail_incomplete.carbon:[[@LINE-34]]:1: note: class was forward declared here
 // CHECK:STDERR: class Class;
 // CHECK:STDERR: ^~~~~~~~~~~~
 // CHECK:STDERR:
@@ -52,7 +52,7 @@ fn G(p: Class*) -> i32 {
   // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+7]]:10: error: member access into object of incomplete type `Class`
   // CHECK:STDERR:   return p->n;
   // CHECK:STDERR:          ^~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-44]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-44]]:1: note: class was forward declared here
   // CHECK:STDERR: class Class;
   // CHECK:STDERR: ^~~~~~~~~~~~
   // CHECK:STDERR:
@@ -63,7 +63,7 @@ fn MemberAccess(p: Class*) -> i32 {
   // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+7]]:11: error: member access into object of incomplete type `Class`
   // CHECK:STDERR:   return (*p).n;
   // CHECK:STDERR:           ^~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-55]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-55]]:1: note: class was forward declared here
   // CHECK:STDERR: class Class;
   // CHECK:STDERR: ^~~~~~~~~~~~
   // CHECK:STDERR:
@@ -73,7 +73,7 @@ fn MemberAccess(p: Class*) -> i32 {
 // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+7]]:20: error: function returns incomplete type `Class`
 // CHECK:STDERR: fn Copy(p: Class*) -> Class {
 // CHECK:STDERR:                    ^~~~~~~~
-// CHECK:STDERR: fail_incomplete.carbon:[[@LINE-65]]:1: class was forward declared here
+// CHECK:STDERR: fail_incomplete.carbon:[[@LINE-65]]:1: note: class was forward declared here
 // CHECK:STDERR: class Class;
 // CHECK:STDERR: ^~~~~~~~~~~~
 // CHECK:STDERR:
@@ -85,7 +85,7 @@ fn Let(p: Class*) {
   // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+7]]:10: error: `let` binding has incomplete type `Class`
   // CHECK:STDERR:   let c: Class = *p;
   // CHECK:STDERR:          ^~~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-77]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-77]]:1: note: class was forward declared here
   // CHECK:STDERR: class Class;
   // CHECK:STDERR: ^~~~~~~~~~~~
   // CHECK:STDERR:
@@ -100,10 +100,10 @@ fn CallTakeIncomplete(p: Class*) {
   // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+10]]:3: error: forming value of incomplete type `Class`
   // CHECK:STDERR:   TakeIncomplete(*p);
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-92]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-92]]:1: note: class was forward declared here
   // CHECK:STDERR: class Class;
   // CHECK:STDERR: ^~~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-11]]:1: initializing parameter 1 of function declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-11]]:1: note: initializing parameter 1 of function declared here
   // CHECK:STDERR: fn TakeIncomplete(c: Class);
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -112,10 +112,10 @@ fn CallTakeIncomplete(p: Class*) {
   // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+10]]:3: error: forming value of incomplete type `Class`
   // CHECK:STDERR:   TakeIncomplete({});
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-104]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-104]]:1: note: class was forward declared here
   // CHECK:STDERR: class Class;
   // CHECK:STDERR: ^~~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-23]]:1: initializing parameter 1 of function declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-23]]:1: note: initializing parameter 1 of function declared here
   // CHECK:STDERR: fn TakeIncomplete(c: Class);
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -126,10 +126,10 @@ fn CallReturnIncomplete() {
   // CHECK:STDERR: fail_incomplete.carbon:[[@LINE+9]]:3: error: function returns incomplete type `Class`
   // CHECK:STDERR:   ReturnIncomplete();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-118]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-118]]:1: note: class was forward declared here
   // CHECK:STDERR: class Class;
   // CHECK:STDERR: ^~~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-35]]:23: return type declared here
+  // CHECK:STDERR: fail_incomplete.carbon:[[@LINE-35]]:23: note: return type declared here
   // CHECK:STDERR: fn ReturnIncomplete() -> Class;
   // CHECK:STDERR:                       ^~~~~~~~
   ReturnIncomplete();

toolchain/check/testdata/class/fail_memaccess_category.carbon

@@ -21,7 +21,7 @@ fn F(s: {.a: A}, b: B) {
   // CHECK:STDERR: fail_memaccess_category.carbon:[[@LINE+7]]:8: error: `addr self` method cannot be invoked on a value
   // CHECK:STDERR:   s.a.F();
   // CHECK:STDERR:        ^
-  // CHECK:STDERR: fail_memaccess_category.carbon:[[@LINE-12]]:13: initializing `addr self` parameter of method declared here
+  // CHECK:STDERR: fail_memaccess_category.carbon:[[@LINE-12]]:13: note: initializing `addr self` parameter of method declared here
   // CHECK:STDERR:   fn F[addr self: A*]();
   // CHECK:STDERR:             ^~~~
   // CHECK:STDERR:
@@ -32,7 +32,7 @@ fn F(s: {.a: A}, b: B) {
   // CHECK:STDERR: fail_memaccess_category.carbon:[[@LINE+6]]:8: error: `addr self` method cannot be invoked on a value
   // CHECK:STDERR:   b.a.F();
   // CHECK:STDERR:        ^
-  // CHECK:STDERR: fail_memaccess_category.carbon:[[@LINE-23]]:13: initializing `addr self` parameter of method declared here
+  // CHECK:STDERR: fail_memaccess_category.carbon:[[@LINE-23]]:13: note: initializing `addr self` parameter of method declared here
   // CHECK:STDERR:   fn F[addr self: A*]();
   // CHECK:STDERR:             ^~~~
   b.a.F();

toolchain/check/testdata/class/fail_member_of_let.carbon

@@ -20,7 +20,7 @@ let T: type = Class;
 // CHECK:STDERR: fail_member_of_let.carbon:[[@LINE+6]]:4: error: name qualifiers are only allowed for entities that provide a scope
 // CHECK:STDERR: fn T.F() {}
 // CHECK:STDERR:    ^
-// CHECK:STDERR: fail_member_of_let.carbon:[[@LINE-7]]:5: referenced non-scope entity declared here
+// CHECK:STDERR: fail_member_of_let.carbon:[[@LINE-7]]:5: note: referenced non-scope entity declared here
 // CHECK:STDERR: let T: type = Class;
 // CHECK:STDERR:     ^
 fn T.F() {}

toolchain/check/testdata/class/fail_method.carbon

@@ -23,7 +23,7 @@ fn F(c: Class) {
   // CHECK:STDERR: fail_method.carbon:[[@LINE+7]]:3: error: missing object argument in method call
   // CHECK:STDERR:   Class.WithSelf();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_method.carbon:[[@LINE-13]]:3: calling function declared here
+  // CHECK:STDERR: fail_method.carbon:[[@LINE-13]]:3: note: calling function declared here
   // CHECK:STDERR:   fn WithSelf[self: Class]();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -31,7 +31,7 @@ fn F(c: Class) {
   // CHECK:STDERR: fail_method.carbon:[[@LINE+7]]:3: error: 1 argument(s) passed to function expecting 0 argument(s).
   // CHECK:STDERR:   Class.WithSelf(c);
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_method.carbon:[[@LINE-21]]:3: calling function declared here
+  // CHECK:STDERR: fail_method.carbon:[[@LINE-21]]:3: note: calling function declared here
   // CHECK:STDERR:   fn WithSelf[self: Class]();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -40,7 +40,7 @@ fn F(c: Class) {
   // CHECK:STDERR: fail_method.carbon:[[@LINE+6]]:3: error: missing object argument in method call
   // CHECK:STDERR:   A();
   // CHECK:STDERR:   ^~
-  // CHECK:STDERR: fail_method.carbon:[[@LINE-30]]:3: calling function declared here
+  // CHECK:STDERR: fail_method.carbon:[[@LINE-30]]:3: note: calling function declared here
   // CHECK:STDERR:   fn WithSelf[self: Class]();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   A();

toolchain/check/testdata/class/fail_method_modifiers.carbon

@@ -13,7 +13,7 @@ class FinalClass {
   // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE+7]]:3: error: `abstract` not allowed on `fn` declaration in a non-abstract `class` definition
   // CHECK:STDERR:   abstract fn Abstract[self: Self]();
   // CHECK:STDERR:   ^~~~~~~~
-  // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE-5]]:1: containing definition here
+  // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE-5]]:1: note: containing definition here
   // CHECK:STDERR: class FinalClass {
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -22,7 +22,7 @@ class FinalClass {
   // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE+7]]:3: error: `virtual` not allowed on `fn` declaration in a non-abstract non-base `class` definition
   // CHECK:STDERR:   virtual fn Virtual[self: Self]();
   // CHECK:STDERR:   ^~~~~~~
-  // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE-14]]:1: containing definition here
+  // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE-14]]:1: note: containing definition here
   // CHECK:STDERR: class FinalClass {
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -49,7 +49,7 @@ base class BaseClass {
   // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE+6]]:3: error: `abstract` not allowed on `fn` declaration in a non-abstract `class` definition
   // CHECK:STDERR:   abstract fn Abstract[self: Self]();
   // CHECK:STDERR:   ^~~~~~~~
-  // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE-5]]:1: containing definition here
+  // CHECK:STDERR: fail_method_modifiers.carbon:[[@LINE-5]]:1: note: containing definition here
   // CHECK:STDERR: base class BaseClass {
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~
   abstract fn Abstract[self: Self]();

toolchain/check/testdata/class/fail_method_redefinition.carbon

@@ -13,7 +13,7 @@ class Class {
   // CHECK:STDERR: fail_method_redefinition.carbon:[[@LINE+6]]:3: error: redefinition of `fn F`
   // CHECK:STDERR:   fn F() {}
   // CHECK:STDERR:   ^~~~~~~~
-  // CHECK:STDERR: fail_method_redefinition.carbon:[[@LINE-4]]:3: previously defined here
+  // CHECK:STDERR: fail_method_redefinition.carbon:[[@LINE-4]]:3: note: previously defined here
   // CHECK:STDERR:   fn F() {}
   // CHECK:STDERR:   ^~~~~~~~
   fn F() {}

toolchain/check/testdata/class/fail_modifiers.carbon

@@ -11,7 +11,7 @@
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:18: error: `private` repeated on declaration
 // CHECK:STDERR: private abstract private class DuplicatePrivate;
 // CHECK:STDERR:                  ^~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `private` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `private` previously appeared here
 // CHECK:STDERR: private abstract private class DuplicatePrivate;
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -20,7 +20,7 @@ private abstract private class DuplicatePrivate;
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:14: error: `protected` not allowed on declaration with `private`
 // CHECK:STDERR: private base protected class TwoAccess {}
 // CHECK:STDERR:              ^~~~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `private` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `private` previously appeared here
 // CHECK:STDERR: private base protected class TwoAccess {}
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -29,7 +29,7 @@ private base protected class TwoAccess {}
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:10: error: `abstract` repeated on declaration
 // CHECK:STDERR: abstract abstract class TwoAbstract;
 // CHECK:STDERR:          ^~~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `abstract` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `abstract` previously appeared here
 // CHECK:STDERR: abstract abstract class TwoAbstract;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -46,7 +46,7 @@ abstract abstract class TwoAbstract;
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:19: error: `base` not allowed on declaration with `virtual`
 // CHECK:STDERR: protected virtual base class Virtual {}
 // CHECK:STDERR:                   ^~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:11: `virtual` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:11: note: `virtual` previously appeared here
 // CHECK:STDERR: protected virtual base class Virtual {}
 // CHECK:STDERR:           ^~~~~~~
 // CHECK:STDERR:
@@ -55,7 +55,7 @@ protected virtual base class Virtual {}
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:10: error: `protected` must appear before `abstract`
 // CHECK:STDERR: abstract protected class WrongOrder;
 // CHECK:STDERR:          ^~~~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `abstract` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `abstract` previously appeared here
 // CHECK:STDERR: abstract protected class WrongOrder;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -64,7 +64,7 @@ abstract protected class WrongOrder;
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+6]]:10: error: `base` not allowed on declaration with `abstract`
 // CHECK:STDERR: abstract base class AbstractAndBase {}
 // CHECK:STDERR:          ^~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+3]]:1: `abstract` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+3]]:1: note: `abstract` previously appeared here
 // CHECK:STDERR: abstract base class AbstractAndBase {}
 // CHECK:STDERR: ^~~~~~~~
 abstract base class AbstractAndBase {}

toolchain/check/testdata/class/fail_redeclaration_introducer.carbon

@@ -16,7 +16,7 @@ class A;
 // CHECK:STDERR: fail_add_base.carbon:[[@LINE+7]]:1: error: class redeclared with different inheritance kind
 // CHECK:STDERR: base class A {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_add_base.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_add_base.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: class A;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -30,7 +30,7 @@ class B;
 // CHECK:STDERR: fail_add_abstract.carbon:[[@LINE+7]]:1: error: class redeclared with different inheritance kind
 // CHECK:STDERR: abstract class B {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_add_abstract.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_add_abstract.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: class B;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -44,7 +44,7 @@ base class C;
 // CHECK:STDERR: fail_remove_base.carbon:[[@LINE+7]]:1: error: class redeclared with different inheritance kind
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
-// CHECK:STDERR: fail_remove_base.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_remove_base.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: base class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -58,7 +58,7 @@ base class D;
 // CHECK:STDERR: fail_base_to_abstract.carbon:[[@LINE+7]]:1: error: class redeclared with different inheritance kind
 // CHECK:STDERR: abstract class D {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_base_to_abstract.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_base_to_abstract.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: base class D;
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -72,7 +72,7 @@ abstract class E;
 // CHECK:STDERR: fail_remove_abstract.carbon:[[@LINE+7]]:1: error: class redeclared with different inheritance kind
 // CHECK:STDERR: class E {}
 // CHECK:STDERR: ^~~~~~~~~
-// CHECK:STDERR: fail_remove_abstract.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_remove_abstract.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: abstract class E;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -86,7 +86,7 @@ abstract class F;
 // CHECK:STDERR: fail_abstract_to_base.carbon:[[@LINE+6]]:1: error: class redeclared with different inheritance kind
 // CHECK:STDERR: base class F {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_abstract_to_base.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_abstract_to_base.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: abstract class F;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
 base class F {}

toolchain/check/testdata/class/fail_redefinition.carbon

@@ -17,7 +17,7 @@ class Class {
 // CHECK:STDERR: fail_redefinition.carbon:[[@LINE+7]]:1: error: redefinition of `class Class`
 // CHECK:STDERR: class Class {
 // CHECK:STDERR: ^~~~~~~~~~~~~
-// CHECK:STDERR: fail_redefinition.carbon:[[@LINE-9]]:1: previously defined here
+// CHECK:STDERR: fail_redefinition.carbon:[[@LINE-9]]:1: note: previously defined here
 // CHECK:STDERR: class Class {
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -37,7 +37,7 @@ fn Class.H() {}
 // CHECK:STDERR: fail_redefinition.carbon:[[@LINE+6]]:1: error: redefinition of `fn I`
 // CHECK:STDERR: fn Class.I() {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redefinition.carbon:[[@LINE-26]]:3: previously defined here
+// CHECK:STDERR: fail_redefinition.carbon:[[@LINE-26]]:3: note: previously defined here
 // CHECK:STDERR:   fn I() {}
 // CHECK:STDERR:   ^~~~~~~~
 fn Class.I() {}

toolchain/check/testdata/class/fail_self.carbon

@@ -46,10 +46,10 @@ fn CallWrongSelf(ws: WrongSelf) {
   // CHECK:STDERR: fail_self.carbon:[[@LINE+9]]:3: error: cannot implicitly convert from `WrongSelf` to `Class`
   // CHECK:STDERR:   ws.F();
   // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_self.carbon:[[@LINE+6]]:3: type `WrongSelf` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_self.carbon:[[@LINE+6]]:3: note: type `WrongSelf` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   ws.F();
   // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_self.carbon:[[@LINE-10]]:8: initializing `self` parameter of method declared here
+  // CHECK:STDERR: fail_self.carbon:[[@LINE-10]]:8: note: initializing `self` parameter of method declared here
   // CHECK:STDERR:   fn F[self: Class]();
   // CHECK:STDERR:        ^~~~
   ws.F();

toolchain/check/testdata/class/generic/call.carbon

@@ -28,7 +28,7 @@ class Class(T:! type, N:! i32) {}
 // CHECK:STDERR: fail_too_few.carbon:[[@LINE+7]]:8: error: 1 argument(s) passed to generic class expecting 2 argument(s).
 // CHECK:STDERR: var a: Class(i32*);
 // CHECK:STDERR:        ^~~~~~
-// CHECK:STDERR: fail_too_few.carbon:[[@LINE-5]]:1: calling generic class declared here
+// CHECK:STDERR: fail_too_few.carbon:[[@LINE-5]]:1: note: calling generic class declared here
 // CHECK:STDERR: class Class(T:! type, N:! i32) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -43,7 +43,7 @@ class Class(T:! type, N:! i32) {}
 // CHECK:STDERR: fail_too_many.carbon:[[@LINE+7]]:8: error: 3 argument(s) passed to generic class expecting 2 argument(s).
 // CHECK:STDERR: var a: Class(i32*, 1, 2);
 // CHECK:STDERR:        ^~~~~~
-// CHECK:STDERR: fail_too_many.carbon:[[@LINE-5]]:1: calling generic class declared here
+// CHECK:STDERR: fail_too_many.carbon:[[@LINE-5]]:1: note: calling generic class declared here
 // CHECK:STDERR: class Class(T:! type, N:! i32) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -58,10 +58,10 @@ class Class(T:! type, N:! i32) {}
 // CHECK:STDERR: fail_no_conversion.carbon:[[@LINE+9]]:8: error: cannot implicitly convert from `i32` to `type`
 // CHECK:STDERR: var a: Class(5, i32*);
 // CHECK:STDERR:        ^~~~~~
-// CHECK:STDERR: fail_no_conversion.carbon:[[@LINE+6]]:8: type `i32` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_no_conversion.carbon:[[@LINE+6]]:8: note: type `i32` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var a: Class(5, i32*);
 // CHECK:STDERR:        ^~~~~~
-// CHECK:STDERR: fail_no_conversion.carbon:[[@LINE-8]]:13: initializing generic parameter `T` declared here
+// CHECK:STDERR: fail_no_conversion.carbon:[[@LINE-8]]:13: note: initializing generic parameter `T` declared here
 // CHECK:STDERR: class Class(T:! type, N:! i32) {}
 // CHECK:STDERR:             ^
 var a: Class(5, i32*);

toolchain/check/testdata/class/generic/import.carbon

@@ -58,7 +58,7 @@ fn Use() {
   // CHECK:STDERR: fail_generic_arg_mismatch.carbon:[[@LINE+7]]:3: error: cannot implicitly convert from `CompleteClass` to `CompleteClass`
   // CHECK:STDERR:   var v: CompleteClass(i32*) = F();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_generic_arg_mismatch.carbon:[[@LINE+4]]:3: type `CompleteClass` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_generic_arg_mismatch.carbon:[[@LINE+4]]:3: note: type `CompleteClass` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   var v: CompleteClass(i32*) = F();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -69,13 +69,11 @@ fn Use() {
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_foo.impl.carbon:[[@LINE+10]]:13: error: redeclaration differs at parameter 1
+// CHECK:STDERR: fail_foo.impl.carbon:[[@LINE+8]]:13: error: redeclaration differs at parameter 1
 // CHECK:STDERR: class Class(U:! type) {
 // CHECK:STDERR:             ^
 // CHECK:STDERR: fail_foo.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "foo";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: foo.carbon:4:13: previous declaration's corresponding parameter here
+// CHECK:STDERR: foo.carbon:4:13: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: class Class(T:! type);
 // CHECK:STDERR:             ^
 // CHECK:STDERR:
@@ -833,8 +831,8 @@ class Class(U:! type) {
 // CHECK:STDOUT:   %default.import.loc2_6.2 = import <invalid>
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %.decl: %.type = class_decl @.1 [template = constants.%.2] {
-// CHECK:STDOUT:     %U.loc14_13.1: type = param U, runtime_param<invalid>
-// CHECK:STDOUT:     %U.loc14_13.2: type = bind_symbolic_name U 0, %U.loc14_13.1 [symbolic = @.1.%U (constants.%U)]
+// CHECK:STDOUT:     %U.loc12_13.1: type = param U, runtime_param<invalid>
+// CHECK:STDOUT:     %U.loc12_13.2: type = bind_symbolic_name U 0, %U.loc12_13.1 [symbolic = @.1.%U (constants.%U)]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -844,19 +842,19 @@ class Class(U:! type) {
 // CHECK:STDOUT:   class;
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: generic class @.1(file.%U.loc14_13.2: type) {
+// CHECK:STDOUT: generic class @.1(file.%U.loc12_13.2: type) {
 // CHECK:STDOUT:   %U: type = bind_symbolic_name U 0 [symbolic = %U (constants.%U)]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !definition:
 // CHECK:STDOUT:
 // CHECK:STDOUT:   class {
 // CHECK:STDOUT:     %T.ref: <error> = name_ref T, <error> [template = <error>]
-// CHECK:STDOUT:     %.loc18: <error> = field_decl x, element0 [template]
-// CHECK:STDOUT:     %.loc19: <witness> = complete_type_witness <error> [template = <error>]
+// CHECK:STDOUT:     %.loc16: <error> = field_decl x, element0 [template]
+// CHECK:STDOUT:     %.loc17: <witness> = complete_type_witness <error> [template = <error>]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   !members:
 // CHECK:STDOUT:     .Self = constants.%.3
-// CHECK:STDOUT:     .x = %.loc18
+// CHECK:STDOUT:     .x = %.loc16
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/class/generic/member_access.carbon

@@ -42,7 +42,7 @@ fn StaticMemberFunctionCall(T:! type) -> Class(T) {
   // CHECK:STDERR: fail_todo_static_member_fn_call.carbon:[[@LINE+6]]:3: error: cannot implicitly convert from `Class` to `Class`
   // CHECK:STDERR:   return Class(T).Make();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_todo_static_member_fn_call.carbon:[[@LINE+3]]:3: type `Class` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_todo_static_member_fn_call.carbon:[[@LINE+3]]:3: note: type `Class` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   return Class(T).Make();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~
   return Class(T).Make();

toolchain/check/testdata/class/generic/member_out_of_line.carbon

@@ -49,7 +49,7 @@ class NotGeneric {
 // CHECK:STDERR: fail_mismatched_not_generic_vs_generic.carbon:[[@LINE+7]]:4: error: redeclaration differs because of parameter list
 // CHECK:STDERR: fn NotGeneric(T:! type).F() {}
 // CHECK:STDERR:    ^~~~~~~~~~
-// CHECK:STDERR: fail_mismatched_not_generic_vs_generic.carbon:[[@LINE-7]]:1: previously declared without parameter list
+// CHECK:STDERR: fail_mismatched_not_generic_vs_generic.carbon:[[@LINE-7]]:1: note: previously declared without parameter list
 // CHECK:STDERR: class NotGeneric {
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -66,7 +66,7 @@ class Generic(T:! type) {
 // CHECK:STDERR: fail_mismatched_too_few_args.carbon:[[@LINE+7]]:4: error: redeclaration differs because of parameter count of 0
 // CHECK:STDERR: fn Generic().TooFew() {}
 // CHECK:STDERR:    ^~~~~~~
-// CHECK:STDERR: fail_mismatched_too_few_args.carbon:[[@LINE-7]]:1: previously declared with parameter count of 1
+// CHECK:STDERR: fail_mismatched_too_few_args.carbon:[[@LINE-7]]:1: note: previously declared with parameter count of 1
 // CHECK:STDERR: class Generic(T:! type) {
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -83,7 +83,7 @@ class Generic(T:! type) {
 // CHECK:STDERR: fail_mismatched_too_many_args.carbon:[[@LINE+7]]:4: error: redeclaration differs because of parameter count of 2
 // CHECK:STDERR: fn Generic(T:! type, U:! type).TooMany() {}
 // CHECK:STDERR:    ^~~~~~~
-// CHECK:STDERR: fail_mismatched_too_many_args.carbon:[[@LINE-7]]:1: previously declared with parameter count of 1
+// CHECK:STDERR: fail_mismatched_too_many_args.carbon:[[@LINE-7]]:1: note: previously declared with parameter count of 1
 // CHECK:STDERR: class Generic(T:! type) {
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -100,7 +100,7 @@ class Generic(T:! type) {
 // CHECK:STDERR: fail_mismatched_wrong_arg_type.carbon:[[@LINE+6]]:12: error: redeclaration differs at parameter 1
 // CHECK:STDERR: fn Generic(T:! ()).WrongType() {}
 // CHECK:STDERR:            ^
-// CHECK:STDERR: fail_mismatched_wrong_arg_type.carbon:[[@LINE-7]]:15: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_mismatched_wrong_arg_type.carbon:[[@LINE-7]]:15: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: class Generic(T:! type) {
 // CHECK:STDERR:               ^
 fn Generic(T:! ()).WrongType() {}

toolchain/check/testdata/class/generic/redeclare.carbon

@@ -25,7 +25,7 @@ class A;
 // CHECK:STDERR: fail_mismatch_param_list.carbon:[[@LINE+7]]:1: error: redeclaration differs because of parameter list
 // CHECK:STDERR: class A(T:! type) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_mismatch_param_list.carbon:[[@LINE-4]]:1: previously declared without parameter list
+// CHECK:STDERR: fail_mismatch_param_list.carbon:[[@LINE-4]]:1: note: previously declared without parameter list
 // CHECK:STDERR: class A;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -39,7 +39,7 @@ class B(N:! i32);
 // CHECK:STDERR: fail_mismatch_implicit_param_list.carbon:[[@LINE+7]]:1: error: redeclaration differs because of implicit parameter list
 // CHECK:STDERR: class B[T:! type](N:! T) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_mismatch_implicit_param_list.carbon:[[@LINE-4]]:1: previously declared without implicit parameter list
+// CHECK:STDERR: fail_mismatch_implicit_param_list.carbon:[[@LINE-4]]:1: note: previously declared without implicit parameter list
 // CHECK:STDERR: class B(N:! i32);
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -53,7 +53,7 @@ class C(T:! type);
 // CHECK:STDERR: fail_mismatch_param_count.carbon:[[@LINE+7]]:1: error: redeclaration differs because of parameter count of 2
 // CHECK:STDERR: class C(T:! type, U:! i32) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_mismatch_param_count.carbon:[[@LINE-4]]:1: previously declared with parameter count of 1
+// CHECK:STDERR: fail_mismatch_param_count.carbon:[[@LINE-4]]:1: note: previously declared with parameter count of 1
 // CHECK:STDERR: class C(T:! type);
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -67,7 +67,7 @@ class D(T:! type);
 // CHECK:STDERR: fail_mismatch_param_type.carbon:[[@LINE+7]]:9: error: redeclaration differs at parameter 1
 // CHECK:STDERR: class D(T:! i32) {}
 // CHECK:STDERR:         ^
-// CHECK:STDERR: fail_mismatch_param_type.carbon:[[@LINE-4]]:9: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_mismatch_param_type.carbon:[[@LINE-4]]:9: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: class D(T:! type);
 // CHECK:STDERR:         ^
 // CHECK:STDERR:
@@ -81,7 +81,7 @@ class E(T:! type);
 // CHECK:STDERR: fail_mismatch_param_name.carbon:[[@LINE+6]]:9: error: redeclaration differs at parameter 1
 // CHECK:STDERR: class E(U:! type) {}
 // CHECK:STDERR:         ^
-// CHECK:STDERR: fail_mismatch_param_name.carbon:[[@LINE-4]]:9: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_mismatch_param_name.carbon:[[@LINE-4]]:9: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: class E(T:! type);
 // CHECK:STDERR:         ^
 class E(U:! type) {}

toolchain/check/testdata/class/inheritance_access.carbon

@@ -82,7 +82,7 @@ class Square {
     // CHECK:STDERR: fail_inherited_private_field_access.carbon:[[@LINE+7]]:12: error: cannot access private member `y` of type `Shape`
     // CHECK:STDERR:     return self.y;
     // CHECK:STDERR:            ^~~~~~
-    // CHECK:STDERR: fail_inherited_private_field_access.carbon:[[@LINE-10]]:15: the private member `y` is defined here
+    // CHECK:STDERR: fail_inherited_private_field_access.carbon:[[@LINE-10]]:15: note: the private member `y` is defined here
     // CHECK:STDERR:   private var y: i32;
     // CHECK:STDERR:               ^~~~~~
     // CHECK:STDERR:
@@ -121,7 +121,7 @@ class C {
   // CHECK:STDERR: fail_noninstance_private_on_parent.carbon:[[@LINE+7]]:12: error: cannot access private member `F` of type `B`
   // CHECK:STDERR:   fn G() { Self.F(); }
   // CHECK:STDERR:            ^~~~~~
-  // CHECK:STDERR: fail_noninstance_private_on_parent.carbon:[[@LINE-8]]:3: the private member `F` is defined here
+  // CHECK:STDERR: fail_noninstance_private_on_parent.carbon:[[@LINE-8]]:3: note: the private member `F` is defined here
   // CHECK:STDERR:   private fn F() {}
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -161,7 +161,7 @@ class B {
     // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE+7]]:5: error: cannot access private member `SOME_PRIVATE_CONSTANT` of type `A`
     // CHECK:STDERR:     A.SOME_PRIVATE_CONSTANT;
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE-14]]:15: the private member `SOME_PRIVATE_CONSTANT` is defined here
+    // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE-14]]:15: note: the private member `SOME_PRIVATE_CONSTANT` is defined here
     // CHECK:STDERR:   private let SOME_PRIVATE_CONSTANT: i32 = 5;
     // CHECK:STDERR:               ^~~~~~~~~~~~~~~~~~~~~
     // CHECK:STDERR:
@@ -170,7 +170,7 @@ class B {
     // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE+7]]:12: error: cannot access protected member `SOME_PROTECTED_CONSTANT` of type `A`
     // CHECK:STDERR:     return A.SOME_PROTECTED_CONSTANT;
     // CHECK:STDERR:            ^~~~~~~~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE-24]]:17: the protected member `SOME_PROTECTED_CONSTANT` is defined here
+    // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE-24]]:17: note: the protected member `SOME_PROTECTED_CONSTANT` is defined here
     // CHECK:STDERR:   protected let SOME_PROTECTED_CONSTANT: i32 = 5;
     // CHECK:STDERR:                 ^~~~~~~~~~~~~~~~~~~~~~~
     // CHECK:STDERR:
@@ -181,7 +181,7 @@ class B {
     // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE+7]]:12: error: cannot access protected member `INTERNAL_CONSTANT` of type `Internal`
     // CHECK:STDERR:     return self.internal.INTERNAL_CONSTANT;
     // CHECK:STDERR:            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE-30]]:17: the protected member `INTERNAL_CONSTANT` is defined here
+    // CHECK:STDERR: fail_non_inherited_access.carbon:[[@LINE-30]]:17: note: the protected member `INTERNAL_CONSTANT` is defined here
     // CHECK:STDERR:   protected let INTERNAL_CONSTANT: i32 = 5;
     // CHECK:STDERR:                 ^~~~~~~~~~~~~~~~~
     // CHECK:STDERR:
@@ -203,7 +203,7 @@ class B {
     // CHECK:STDERR: fail_compound_member_access.carbon:[[@LINE+6]]:11: error: cannot access private member `x` of type `A`
     // CHECK:STDERR:     self.(A.x);
     // CHECK:STDERR:           ^~~
-    // CHECK:STDERR: fail_compound_member_access.carbon:[[@LINE-9]]:15: the private member `x` is defined here
+    // CHECK:STDERR: fail_compound_member_access.carbon:[[@LINE-9]]:15: note: the private member `x` is defined here
     // CHECK:STDERR:   private var x: i32;
     // CHECK:STDERR:               ^~~~~~
     self.(A.x);

toolchain/check/testdata/class/init_adapt.carbon

@@ -55,7 +55,7 @@ let a: C = {.a = 1, .b = 2};
 // CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+7]]:1: error: cannot implicitly convert from `C` to `AdaptC`
 // CHECK:STDERR: let b: AdaptC = a;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+4]]:1: type `C` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+4]]:1: note: type `C` does not implement interface `ImplicitAs`
 // CHECK:STDERR: let b: AdaptC = a;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -64,7 +64,7 @@ let b: AdaptC = a;
 // CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+7]]:1: error: cannot implicitly convert from `AdaptC` to `C`
 // CHECK:STDERR: let c: C = b;
 // CHECK:STDERR: ^~~~~~~~~~~~~
-// CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+4]]:1: type `<error>` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+4]]:1: note: type `<error>` does not implement interface `ImplicitAs`
 // CHECK:STDERR: let c: C = b;
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -77,7 +77,7 @@ fn MakeAdaptC() -> AdaptC;
 // CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+7]]:1: error: cannot implicitly convert from `C` to `AdaptC`
 // CHECK:STDERR: var d: AdaptC = MakeC();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+4]]:1: type `C` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+4]]:1: note: type `C` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var d: AdaptC = MakeC();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -86,7 +86,7 @@ var d: AdaptC = MakeC();
 // CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+6]]:1: error: cannot implicitly convert from `AdaptC` to `C`
 // CHECK:STDERR: var e: C = MakeAdaptC();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+3]]:1: type `AdaptC` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_not_implicit.carbon:[[@LINE+3]]:1: note: type `AdaptC` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var e: C = MakeAdaptC();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~
 var e: C = MakeAdaptC();

toolchain/check/testdata/class/no_prelude/extern.carbon

@@ -48,7 +48,7 @@ extern class C;
 // CHECK:STDERR: fail_decl_fn_in_extern.carbon:[[@LINE+7]]:4: error: cannot declare a member of incomplete class `C`
 // CHECK:STDERR: fn C.F();
 // CHECK:STDERR:    ^
-// CHECK:STDERR: fail_decl_fn_in_extern.carbon:[[@LINE-4]]:1: class was forward declared here
+// CHECK:STDERR: fail_decl_fn_in_extern.carbon:[[@LINE-4]]:1: note: class was forward declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -68,7 +68,7 @@ extern class C;
 // CHECK:STDERR: fail_extern_decl_after_extern_decl.carbon:[[@LINE+7]]:1: error: redeclaration of `class C` is redundant
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_extern_decl_after_extern_decl.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_extern_decl_after_extern_decl.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -82,7 +82,7 @@ extern class C;
 // CHECK:STDERR: fail_decl_after_extern_decl.carbon:[[@LINE+7]]:1: error: redeclaration of `class C` is redundant
 // CHECK:STDERR: class C;
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_decl_after_extern_decl.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_decl_after_extern_decl.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -108,7 +108,7 @@ extern class C;
 // CHECK:STDERR: fail_def_after_extern_decl.carbon:[[@LINE+7]]:1: error: redeclarations of `class C` must match use of `extern`
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
-// CHECK:STDERR: fail_def_after_extern_decl.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_def_after_extern_decl.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -122,7 +122,7 @@ class C;
 // CHECK:STDERR: fail_extern_decl_after_decl.carbon:[[@LINE+7]]:1: error: redeclaration of `class C` is redundant
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_extern_decl_after_decl.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_extern_decl_after_decl.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: class C;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -132,16 +132,12 @@ extern class C;
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_import_extern_decl_then_decl.carbon:[[@LINE+13]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_import_extern_decl_then_decl.carbon:[[@LINE+9]]:1: in import
 // CHECK:STDERR: decl.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: class C;
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_import_extern_decl_then_decl.carbon:[[@LINE+7]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_decl.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_import_extern_decl_then_decl.carbon:[[@LINE+5]]:1: in import
+// CHECK:STDERR: extern_decl.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -152,16 +148,12 @@ import library "decl";
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_import_decl_then_extern_decl.carbon:[[@LINE+13]]:1: in import
-// CHECK:STDERR: import library "decl";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_import_decl_then_extern_decl.carbon:[[@LINE+9]]:1: in import
 // CHECK:STDERR: extern_decl.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_import_decl_then_extern_decl.carbon:[[@LINE+7]]:1: in import
-// CHECK:STDERR: import library "decl";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: decl.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_import_decl_then_extern_decl.carbon:[[@LINE+5]]:1: in import
+// CHECK:STDERR: decl.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: class C;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -172,16 +164,12 @@ import library "extern_decl";
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_import_extern_decl_then_def.carbon:[[@LINE+13]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_import_extern_decl_then_def.carbon:[[@LINE+9]]:1: in import
 // CHECK:STDERR: def.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
-// CHECK:STDERR: fail_import_extern_decl_then_def.carbon:[[@LINE+7]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_decl.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_import_extern_decl_then_def.carbon:[[@LINE+5]]:1: in import
+// CHECK:STDERR: extern_decl.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -192,29 +180,21 @@ import library "def";
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_import_ownership_conflict.carbon:[[@LINE+26]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_import_ownership_conflict.carbon:[[@LINE+18]]:1: in import
 // CHECK:STDERR: decl.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: class C;
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_import_ownership_conflict.carbon:[[@LINE+20]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_decl.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_import_ownership_conflict.carbon:[[@LINE+14]]:1: in import
+// CHECK:STDERR: extern_decl.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_import_ownership_conflict.carbon:[[@LINE+13]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_import_ownership_conflict.carbon:[[@LINE+9]]:1: in import
 // CHECK:STDERR: def.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
-// CHECK:STDERR: fail_import_ownership_conflict.carbon:[[@LINE+7]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_decl.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_import_ownership_conflict.carbon:[[@LINE+5]]:1: in import
+// CHECK:STDERR: extern_decl.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -226,16 +206,12 @@ import library "def";
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_todo_import_extern_decl_copy.carbon:[[@LINE+13]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_todo_import_extern_decl_copy.carbon:[[@LINE+9]]:1: in import
 // CHECK:STDERR: extern_decl_copy.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_todo_import_extern_decl_copy.carbon:[[@LINE+7]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_decl.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_todo_import_extern_decl_copy.carbon:[[@LINE+5]]:1: in import
+// CHECK:STDERR: extern_decl.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -248,13 +224,11 @@ library "[[@TEST_NAME]]";
 
 import library "extern_decl";
 
-// CHECK:STDERR: fail_extern_decl_after_import_extern_decl.carbon:[[@LINE+10]]:1: error: redeclaration of `class C` is redundant
+// CHECK:STDERR: fail_extern_decl_after_import_extern_decl.carbon:[[@LINE+8]]:1: error: redeclaration of `class C` is redundant
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_extern_decl_after_import_extern_decl.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "extern_decl";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_decl.carbon:4:1: previously declared here
+// CHECK:STDERR: extern_decl.carbon:4:1: note: previously declared here
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -266,13 +240,11 @@ library "[[@TEST_NAME]]";
 
 import library "decl";
 
-// CHECK:STDERR: fail_decl_after_import_extern_decl.carbon:[[@LINE+10]]:1: error: redeclarations of `class C` must match use of `extern`
+// CHECK:STDERR: fail_decl_after_import_extern_decl.carbon:[[@LINE+8]]:1: error: redeclarations of `class C` must match use of `extern`
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_decl_after_import_extern_decl.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "decl";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: decl.carbon:4:1: previously declared here
+// CHECK:STDERR: decl.carbon:4:1: note: previously declared here
 // CHECK:STDERR: class C;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -284,13 +256,11 @@ library "[[@TEST_NAME]]";
 
 import library "def";
 
-// CHECK:STDERR: fail_def_after_import_extern_decl.carbon:[[@LINE+10]]:1: error: redeclarations of `class C` must match use of `extern`
+// CHECK:STDERR: fail_def_after_import_extern_decl.carbon:[[@LINE+8]]:1: error: redeclarations of `class C` must match use of `extern`
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_def_after_import_extern_decl.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "def";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: def.carbon:4:1: previously declared here
+// CHECK:STDERR: def.carbon:4:1: note: previously declared here
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
 // CHECK:STDERR:
@@ -302,13 +272,11 @@ library "[[@TEST_NAME]]";
 
 import library "def";
 
-// CHECK:STDERR: fail_extern_decl_after_import_def.carbon:[[@LINE+9]]:1: error: redeclarations of `class C` must match use of `extern`
+// CHECK:STDERR: fail_extern_decl_after_import_def.carbon:[[@LINE+7]]:1: error: redeclarations of `class C` must match use of `extern`
 // CHECK:STDERR: extern class C;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_extern_decl_after_import_def.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "def";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: def.carbon:4:1: previously declared here
+// CHECK:STDERR: def.carbon:4:1: note: previously declared here
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
 extern class C;

toolchain/check/testdata/class/no_prelude/implicit_import.carbon

@@ -30,13 +30,11 @@ class C {}
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_redecl_after_def.impl.carbon:[[@LINE+10]]:1: error: redeclaration of `class C` is redundant
+// CHECK:STDERR: fail_redecl_after_def.impl.carbon:[[@LINE+8]]:1: error: redeclaration of `class C` is redundant
 // CHECK:STDERR: class C;
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR: fail_redecl_after_def.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "redecl_after_def";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: redecl_after_def.carbon:4:1: previously declared here
+// CHECK:STDERR: redecl_after_def.carbon:4:1: note: previously declared here
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
 // CHECK:STDERR:
@@ -52,13 +50,11 @@ class C {}
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_redef_after_def.impl.carbon:[[@LINE+10]]:1: error: redefinition of `class C`
+// CHECK:STDERR: fail_redef_after_def.impl.carbon:[[@LINE+8]]:1: error: redefinition of `class C`
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
 // CHECK:STDERR: fail_redef_after_def.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "redef_after_def";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: redef_after_def.carbon:4:1: previously defined here
+// CHECK:STDERR: redef_after_def.carbon:4:1: note: previously defined here
 // CHECK:STDERR: class C {}
 // CHECK:STDERR: ^~~~~~~~~
 // CHECK:STDERR:
@@ -75,13 +71,11 @@ alias B = C;
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_def_alias.impl.carbon:[[@LINE+9]]:1: error: duplicate name being declared in the same scope
+// CHECK:STDERR: fail_def_alias.impl.carbon:[[@LINE+7]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: class B {}
 // CHECK:STDERR: ^~~~~~~~~
 // CHECK:STDERR: fail_def_alias.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "def_alias";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: def_alias.carbon:5:7: name is previously declared here
+// CHECK:STDERR: def_alias.carbon:5:7: note: name is previously declared here
 // CHECK:STDERR: alias B = C;
 // CHECK:STDERR:       ^
 class B {}
@@ -229,7 +223,7 @@ class B {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @.1 {
-// CHECK:STDOUT:   %.loc14: <witness> = complete_type_witness %.1 [template = constants.%.2]
+// CHECK:STDOUT:   %.loc12: <witness> = complete_type_witness %.1 [template = constants.%.2]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = constants.%.3
@@ -280,7 +274,7 @@ class B {}
 // CHECK:STDOUT: class @C;
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @.1 {
-// CHECK:STDOUT:   %.loc13: <witness> = complete_type_witness %.2 [template = constants.%.3]
+// CHECK:STDOUT:   %.loc11: <witness> = complete_type_witness %.2 [template = constants.%.3]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = constants.%.1

toolchain/check/testdata/class/no_prelude/syntactic_merge.carbon

@@ -40,7 +40,7 @@ class Foo(a:! C);
 // CHECK:STDERR: fail_parens.carbon:[[@LINE+7]]:15: error: redeclaration syntax differs here
 // CHECK:STDERR: class Foo(a:! (C)) {}
 // CHECK:STDERR:               ^
-// CHECK:STDERR: fail_parens.carbon:[[@LINE-4]]:15: comparing with previous declaration here
+// CHECK:STDERR: fail_parens.carbon:[[@LINE-4]]:15: note: comparing with previous declaration here
 // CHECK:STDERR: class Foo(a:! C);
 // CHECK:STDERR:               ^
 // CHECK:STDERR:
@@ -83,7 +83,7 @@ class Foo(a:! C);
 // CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE+7]]:11: error: redeclaration differs at parameter 1
 // CHECK:STDERR: class Foo(b:! D) {}
 // CHECK:STDERR:           ^
-// CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE-4]]:11: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE-4]]:11: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: class Foo(a:! C);
 // CHECK:STDERR:           ^
 // CHECK:STDERR:
@@ -100,7 +100,7 @@ class Foo(a:! C);
 // CHECK:STDERR: fail_alias.carbon:[[@LINE+7]]:15: error: redeclaration syntax differs here
 // CHECK:STDERR: class Foo(a:! D) {}
 // CHECK:STDERR:               ^
-// CHECK:STDERR: fail_alias.carbon:[[@LINE-4]]:15: comparing with previous declaration here
+// CHECK:STDERR: fail_alias.carbon:[[@LINE-4]]:15: note: comparing with previous declaration here
 // CHECK:STDERR: class Foo(a:! C);
 // CHECK:STDERR:               ^
 // CHECK:STDERR:
@@ -117,7 +117,7 @@ class Foo[a:! C]();
 // CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE+7]]:15: error: redeclaration syntax differs here
 // CHECK:STDERR: class Foo[a:! D]() {}
 // CHECK:STDERR:               ^
-// CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE-4]]:15: comparing with previous declaration here
+// CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE-4]]:15: note: comparing with previous declaration here
 // CHECK:STDERR: class Foo[a:! C]();
 // CHECK:STDERR:               ^
 // CHECK:STDERR:
@@ -153,7 +153,7 @@ class Foo(a:! const C);
 // CHECK:STDERR: fail_repeat_const.carbon:[[@LINE+7]]:21: error: redeclaration syntax differs here
 // CHECK:STDERR: class Foo(a:! const (const C)) {}
 // CHECK:STDERR:                     ^
-// CHECK:STDERR: fail_repeat_const.carbon:[[@LINE-8]]:21: comparing with previous declaration here
+// CHECK:STDERR: fail_repeat_const.carbon:[[@LINE-8]]:21: note: comparing with previous declaration here
 // CHECK:STDERR: class Foo(a:! const C);
 // CHECK:STDERR:                     ^
 // CHECK:STDERR:
@@ -172,7 +172,7 @@ base class Base {
 // CHECK:STDERR: fail_self_type.carbon:[[@LINE+6]]:22: error: redeclaration syntax differs here
 // CHECK:STDERR: fn Base.F[addr self: Base*]() {
 // CHECK:STDERR:                      ^~~~
-// CHECK:STDERR: fail_self_type.carbon:[[@LINE-6]]:19: comparing with previous declaration here
+// CHECK:STDERR: fail_self_type.carbon:[[@LINE-6]]:19: note: comparing with previous declaration here
 // CHECK:STDERR:   fn F[addr self: Self*]();
 // CHECK:STDERR:                   ^~~~
 fn Base.F[addr self: Base*]() {

toolchain/check/testdata/class/syntactic_merge_literal.carbon

@@ -23,7 +23,7 @@ class D(b:! C(1000));
 // CHECK:STDERR: fail_int_mismatch.carbon:[[@LINE+6]]:15: error: redeclaration syntax differs here
 // CHECK:STDERR: class D(b:! C(1_000)) {}
 // CHECK:STDERR:               ^~~~~
-// CHECK:STDERR: fail_int_mismatch.carbon:[[@LINE-4]]:15: comparing with previous declaration here
+// CHECK:STDERR: fail_int_mismatch.carbon:[[@LINE-4]]:15: note: comparing with previous declaration here
 // CHECK:STDERR: class D(b:! C(1000));
 // CHECK:STDERR:               ^~~~
 class D(b:! C(1_000)) {}

toolchain/check/testdata/const/fail_collapse.carbon

@@ -16,7 +16,7 @@ fn G(p: const (const i32)**) -> i32** {
   // CHECK:STDERR: fail_collapse.carbon:[[@LINE+6]]:3: error: cannot implicitly convert from `const i32**` to `i32**`
   // CHECK:STDERR:   return p;
   // CHECK:STDERR:   ^~~~~~~~~
-  // CHECK:STDERR: fail_collapse.carbon:[[@LINE+3]]:3: type `const i32**` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_collapse.carbon:[[@LINE+3]]:3: note: type `const i32**` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   return p;
   // CHECK:STDERR:   ^~~~~~~~~
   return p;

toolchain/check/testdata/function/builtin/fail_redefined.carbon

@@ -12,7 +12,7 @@ fn A(n: i32, m: i32) -> i32 = "int.sadd";
 // CHECK:STDERR: fail_redefined.carbon:[[@LINE+7]]:1: error: redefinition of `fn A`
 // CHECK:STDERR: fn A(n: i32, m: i32) -> i32 { return n; }
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redefined.carbon:[[@LINE-4]]:1: previously defined here
+// CHECK:STDERR: fail_redefined.carbon:[[@LINE-4]]:1: note: previously defined here
 // CHECK:STDERR: fn A(n: i32, m: i32) -> i32 = "int.sadd";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -22,7 +22,7 @@ fn B(n: i32, m: i32) -> i32 { return n; }
 // CHECK:STDERR: fail_redefined.carbon:[[@LINE+7]]:1: error: redefinition of `fn B`
 // CHECK:STDERR: fn B(n: i32, m: i32) -> i32 = "int.sadd";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redefined.carbon:[[@LINE-4]]:1: previously defined here
+// CHECK:STDERR: fail_redefined.carbon:[[@LINE-4]]:1: note: previously defined here
 // CHECK:STDERR: fn B(n: i32, m: i32) -> i32 { return n; }
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -32,7 +32,7 @@ fn C(n: i32, m: i32) -> i32 = "int.sadd";
 // CHECK:STDERR: fail_redefined.carbon:[[@LINE+6]]:1: error: redefinition of `fn C`
 // CHECK:STDERR: fn C(n: i32, m: i32) -> i32 = "int.sadd";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redefined.carbon:[[@LINE-4]]:1: previously defined here
+// CHECK:STDERR: fail_redefined.carbon:[[@LINE-4]]:1: note: previously defined here
 // CHECK:STDERR: fn C(n: i32, m: i32) -> i32 = "int.sadd";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 fn C(n: i32, m: i32) -> i32 = "int.sadd";

toolchain/check/testdata/function/call/fail_param_count.carbon

@@ -16,7 +16,7 @@ fn Main() {
   // CHECK:STDERR: fail_param_count.carbon:[[@LINE+7]]:3: error: 1 argument(s) passed to function expecting 0 argument(s).
   // CHECK:STDERR:   Run0(1);
   // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-8]]:1: calling function declared here
+  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-8]]:1: note: calling function declared here
   // CHECK:STDERR: fn Run0() {}
   // CHECK:STDERR: ^~~~~~~~~~~
   // CHECK:STDERR:
@@ -24,7 +24,7 @@ fn Main() {
   // CHECK:STDERR: fail_param_count.carbon:[[@LINE+7]]:3: error: 2 argument(s) passed to function expecting 0 argument(s).
   // CHECK:STDERR:   Run0(0, 1);
   // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-16]]:1: calling function declared here
+  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-16]]:1: note: calling function declared here
   // CHECK:STDERR: fn Run0() {}
   // CHECK:STDERR: ^~~~~~~~~~~
   // CHECK:STDERR:
@@ -33,7 +33,7 @@ fn Main() {
   // CHECK:STDERR: fail_param_count.carbon:[[@LINE+7]]:3: error: 0 argument(s) passed to function expecting 1 argument(s).
   // CHECK:STDERR:   Run1();
   // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-24]]:1: calling function declared here
+  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-24]]:1: note: calling function declared here
   // CHECK:STDERR: fn Run1(a: i32) {}
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -41,7 +41,7 @@ fn Main() {
   // CHECK:STDERR: fail_param_count.carbon:[[@LINE+7]]:3: error: 2 argument(s) passed to function expecting 1 argument(s).
   // CHECK:STDERR:   Run1(0, 1);
   // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-32]]:1: calling function declared here
+  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-32]]:1: note: calling function declared here
   // CHECK:STDERR: fn Run1(a: i32) {}
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -50,7 +50,7 @@ fn Main() {
   // CHECK:STDERR: fail_param_count.carbon:[[@LINE+7]]:3: error: 0 argument(s) passed to function expecting 2 argument(s).
   // CHECK:STDERR:   Run2();
   // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-40]]:1: calling function declared here
+  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-40]]:1: note: calling function declared here
   // CHECK:STDERR: fn Run2(a: i32, b: i32) {}
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -58,7 +58,7 @@ fn Main() {
   // CHECK:STDERR: fail_param_count.carbon:[[@LINE+6]]:3: error: 1 argument(s) passed to function expecting 2 argument(s).
   // CHECK:STDERR:   Run2(0);
   // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-48]]:1: calling function declared here
+  // CHECK:STDERR: fail_param_count.carbon:[[@LINE-48]]:1: note: calling function declared here
   // CHECK:STDERR: fn Run2(a: i32, b: i32) {}
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
   Run2(0);

toolchain/check/testdata/function/call/fail_param_type.carbon

@@ -14,10 +14,10 @@ fn F() {
   // CHECK:STDERR: fail_param_type.carbon:[[@LINE+9]]:3: error: cannot implicitly convert from `f64` to `i32`
   // CHECK:STDERR:   G(1.0);
   // CHECK:STDERR:   ^~
-  // CHECK:STDERR: fail_param_type.carbon:[[@LINE+6]]:3: type `f64` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_param_type.carbon:[[@LINE+6]]:3: note: type `f64` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   G(1.0);
   // CHECK:STDERR:   ^~
-  // CHECK:STDERR: fail_param_type.carbon:[[@LINE-9]]:1: initializing parameter 1 of function declared here
+  // CHECK:STDERR: fail_param_type.carbon:[[@LINE-9]]:1: note: initializing parameter 1 of function declared here
   // CHECK:STDERR: fn G(a: i32) {}
   // CHECK:STDERR: ^~~~~~~~~~~~~~
   G(1.0);

toolchain/check/testdata/function/call/fail_return_type_mismatch.carbon

@@ -14,7 +14,7 @@ fn Run() {
   // CHECK:STDERR: fail_return_type_mismatch.carbon:[[@LINE+6]]:3: error: cannot implicitly convert from `f64` to `i32`
   // CHECK:STDERR:   var x: i32 = Foo();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_return_type_mismatch.carbon:[[@LINE+3]]:3: type `f64` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_return_type_mismatch.carbon:[[@LINE+3]]:3: note: type `f64` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   var x: i32 = Foo();
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~
   var x: i32 = Foo();

toolchain/check/testdata/function/declaration/fail_param_redecl.carbon

@@ -11,7 +11,7 @@
 // CHECK:STDERR: fail_param_redecl.carbon:[[@LINE+6]]:14: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn F(n: i32, n: i32);
 // CHECK:STDERR:              ^
-// CHECK:STDERR: fail_param_redecl.carbon:[[@LINE+3]]:6: name is previously declared here
+// CHECK:STDERR: fail_param_redecl.carbon:[[@LINE+3]]:6: note: name is previously declared here
 // CHECK:STDERR: fn F(n: i32, n: i32);
 // CHECK:STDERR:      ^
 fn F(n: i32, n: i32);

toolchain/check/testdata/function/declaration/import.carbon

@@ -58,57 +58,47 @@ library "[[@TEST_NAME]]";
 
 import library "api";
 
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+10]]:1: error: redeclarations of `fn A` must match use of `extern`
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+8]]:1: error: redeclarations of `fn A` must match use of `extern`
 // CHECK:STDERR: extern fn A();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:4:1: previously declared here
+// CHECK:STDERR: api.carbon:4:1: note: previously declared here
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
 extern fn A();
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+10]]:1: error: redeclarations of `fn B` must match use of `extern`
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+8]]:1: error: redeclarations of `fn B` must match use of `extern`
 // CHECK:STDERR: extern fn B(b: i32) -> i32;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-16]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:5:1: previously declared here
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-14]]:1: in import
+// CHECK:STDERR: api.carbon:5:1: note: previously declared here
 // CHECK:STDERR: fn B(b: i32) -> i32;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
 extern fn B(b: i32) -> i32;
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+10]]:1: error: redeclarations of `fn C` must match use of `extern`
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+8]]:1: error: redeclarations of `fn C` must match use of `extern`
 // CHECK:STDERR: extern fn C(c: (i32,)) -> {.c: i32};
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-27]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:6:1: previously declared here
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-23]]:1: in import
+// CHECK:STDERR: api.carbon:6:1: note: previously declared here
 // CHECK:STDERR: fn C(c: (i32,)) -> {.c: i32};
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
 extern fn C(c: (i32,)) -> {.c: i32};
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+10]]:1: error: redeclaration of `fn D` is redundant
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+8]]:1: error: redeclaration of `fn D` is redundant
 // CHECK:STDERR: extern fn D();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-38]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:7:1: previously declared here
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-32]]:1: in import
+// CHECK:STDERR: api.carbon:7:1: note: previously declared here
 // CHECK:STDERR: extern fn D();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
 extern fn D();
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+10]]:1: error: redeclarations of `fn E` must match use of `extern`
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE+8]]:1: error: redeclarations of `fn E` must match use of `extern`
 // CHECK:STDERR: extern fn NS.E();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-49]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:10:1: previously declared here
+// CHECK:STDERR: fail_redecl_api.carbon:[[@LINE-41]]:1: in import
+// CHECK:STDERR: api.carbon:10:1: note: previously declared here
 // CHECK:STDERR: fn NS.E();
 // CHECK:STDERR: ^~~~~~~~~~
 // CHECK:STDERR:
@@ -142,68 +132,48 @@ var e: () = NS.E();
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+65]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+45]]:1: in import
 // CHECK:STDERR: extern_api.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern library "redecl_extern_api" fn A();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+59]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+41]]:1: in import
+// CHECK:STDERR: api.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+52]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+36]]:1: in import
 // CHECK:STDERR: extern_api.carbon:5:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern library "redecl_extern_api" fn B(b: i32) -> i32;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+46]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:5:1: name is previously declared here
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+32]]:1: in import
+// CHECK:STDERR: api.carbon:5:1: note: name is previously declared here
 // CHECK:STDERR: fn B(b: i32) -> i32;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+39]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+27]]:1: in import
 // CHECK:STDERR: extern_api.carbon:6:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern library "redecl_extern_api" fn C(c: (i32,)) -> {.c: i32};
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+33]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:6:1: name is previously declared here
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+23]]:1: in import
+// CHECK:STDERR: api.carbon:6:1: note: name is previously declared here
 // CHECK:STDERR: fn C(c: (i32,)) -> {.c: i32};
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+26]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+18]]:1: in import
 // CHECK:STDERR: extern_api.carbon:7:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern library "redecl_extern_api" fn D();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+20]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:7:1: name is previously declared here
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+14]]:1: in import
+// CHECK:STDERR: api.carbon:7:1: note: name is previously declared here
 // CHECK:STDERR: extern fn D();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+13]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+9]]:1: in import
 // CHECK:STDERR: extern_api.carbon:10:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern library "redecl_extern_api" fn NS.E();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_merge.carbon:[[@LINE+7]]:1: in import
-// CHECK:STDERR: import library "api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: api.carbon:10:1: name is previously declared here
+// CHECK:STDERR: fail_merge.carbon:[[@LINE+5]]:1: in import
+// CHECK:STDERR: api.carbon:10:1: note: name is previously declared here
 // CHECK:STDERR: fn NS.E();
 // CHECK:STDERR: ^~~~~~~~~~
 // CHECK:STDERR:
@@ -220,68 +190,48 @@ var e: () = NS.E();
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+64]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+44]]:1: in import
 // CHECK:STDERR: api.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+58]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_api.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+40]]:1: in import
+// CHECK:STDERR: extern_api.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: extern library "redecl_extern_api" fn A();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+51]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+35]]:1: in import
 // CHECK:STDERR: api.carbon:5:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn B(b: i32) -> i32;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+45]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_api.carbon:5:1: name is previously declared here
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+31]]:1: in import
+// CHECK:STDERR: extern_api.carbon:5:1: note: name is previously declared here
 // CHECK:STDERR: extern library "redecl_extern_api" fn B(b: i32) -> i32;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+38]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+26]]:1: in import
 // CHECK:STDERR: api.carbon:6:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn C(c: (i32,)) -> {.c: i32};
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+32]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_api.carbon:6:1: name is previously declared here
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+22]]:1: in import
+// CHECK:STDERR: extern_api.carbon:6:1: note: name is previously declared here
 // CHECK:STDERR: extern library "redecl_extern_api" fn C(c: (i32,)) -> {.c: i32};
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+25]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+17]]:1: in import
 // CHECK:STDERR: api.carbon:7:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern fn D();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+19]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_api.carbon:7:1: name is previously declared here
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+13]]:1: in import
+// CHECK:STDERR: extern_api.carbon:7:1: note: name is previously declared here
 // CHECK:STDERR: extern library "redecl_extern_api" fn D();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+12]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+8]]:1: in import
 // CHECK:STDERR: api.carbon:10:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn NS.E();
 // CHECK:STDERR: ^~~~~~~~~~
-// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+6]]:1: in import
-// CHECK:STDERR: import library "extern_api";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_api.carbon:10:1: name is previously declared here
+// CHECK:STDERR: fail_merge_reverse.carbon:[[@LINE+4]]:1: in import
+// CHECK:STDERR: extern_api.carbon:10:1: note: name is previously declared here
 // CHECK:STDERR: extern library "redecl_extern_api" fn NS.E();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 import library "extern_api";
@@ -668,8 +618,8 @@ import library "extern_api";
 // CHECK:STDOUT:     .NS = imports.%NS
 // CHECK:STDOUT:     .Core = imports.%Core
 // CHECK:STDOUT:     .a = %a
-// CHECK:STDOUT:     .b = %b.loc63
-// CHECK:STDOUT:     .c = %c.loc64
+// CHECK:STDOUT:     .b = %b.loc53
+// CHECK:STDOUT:     .c = %c.loc54
 // CHECK:STDOUT:     .d = %d
 // CHECK:STDOUT:     .e = %e
 // CHECK:STDOUT:   }
@@ -677,53 +627,53 @@ import library "extern_api";
 // CHECK:STDOUT:   %default.import = import <invalid>
 // CHECK:STDOUT:   %A.decl: %A.type = fn_decl @A [template = constants.%A] {}
 // CHECK:STDOUT:   %B.decl: %B.type = fn_decl @B [template = constants.%B] {
-// CHECK:STDOUT:     %int.make_type_32.loc27_16: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:     %.loc27_16.1: type = value_of_initializer %int.make_type_32.loc27_16 [template = i32]
-// CHECK:STDOUT:     %.loc27_16.2: type = converted %int.make_type_32.loc27_16, %.loc27_16.1 [template = i32]
-// CHECK:STDOUT:     %b.loc27_13.1: i32 = param b, runtime_param0
-// CHECK:STDOUT:     %b.loc27_13.2: i32 = bind_name b, %b.loc27_13.1
-// CHECK:STDOUT:     %int.make_type_32.loc27_24: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:     %.loc27_24.1: type = value_of_initializer %int.make_type_32.loc27_24 [template = i32]
-// CHECK:STDOUT:     %.loc27_24.2: type = converted %int.make_type_32.loc27_24, %.loc27_24.1 [template = i32]
-// CHECK:STDOUT:     %return.var.loc27: ref i32 = var <return slot>
+// CHECK:STDOUT:     %int.make_type_32.loc23_16: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:     %.loc23_16.1: type = value_of_initializer %int.make_type_32.loc23_16 [template = i32]
+// CHECK:STDOUT:     %.loc23_16.2: type = converted %int.make_type_32.loc23_16, %.loc23_16.1 [template = i32]
+// CHECK:STDOUT:     %b.loc23_13.1: i32 = param b, runtime_param0
+// CHECK:STDOUT:     %b.loc23_13.2: i32 = bind_name b, %b.loc23_13.1
+// CHECK:STDOUT:     %int.make_type_32.loc23_24: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:     %.loc23_24.1: type = value_of_initializer %int.make_type_32.loc23_24 [template = i32]
+// CHECK:STDOUT:     %.loc23_24.2: type = converted %int.make_type_32.loc23_24, %.loc23_24.1 [template = i32]
+// CHECK:STDOUT:     %return.var.loc23: ref i32 = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %C.decl: %C.type = fn_decl @C [template = constants.%C] {
-// CHECK:STDOUT:     %int.make_type_32.loc38_17: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:     %.loc38_21.1: %.2 = tuple_literal (%int.make_type_32.loc38_17)
-// CHECK:STDOUT:     %.loc38_21.2: type = value_of_initializer %int.make_type_32.loc38_17 [template = i32]
-// CHECK:STDOUT:     %.loc38_21.3: type = converted %int.make_type_32.loc38_17, %.loc38_21.2 [template = i32]
-// CHECK:STDOUT:     %.loc38_21.4: type = converted %.loc38_21.1, constants.%.3 [template = constants.%.3]
-// CHECK:STDOUT:     %c.loc38_13.1: %.3 = param c, runtime_param0
-// CHECK:STDOUT:     %c.loc38_13.2: %.3 = bind_name c, %c.loc38_13.1
-// CHECK:STDOUT:     %int.make_type_32.loc38_32: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:     %.loc38_32.1: type = value_of_initializer %int.make_type_32.loc38_32 [template = i32]
-// CHECK:STDOUT:     %.loc38_32.2: type = converted %int.make_type_32.loc38_32, %.loc38_32.1 [template = i32]
-// CHECK:STDOUT:     %.loc38_35: type = struct_type {.c: i32} [template = constants.%.4]
-// CHECK:STDOUT:     %return.var.loc38: ref %.4 = var <return slot>
+// CHECK:STDOUT:     %int.make_type_32.loc32_17: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:     %.loc32_21.1: %.2 = tuple_literal (%int.make_type_32.loc32_17)
+// CHECK:STDOUT:     %.loc32_21.2: type = value_of_initializer %int.make_type_32.loc32_17 [template = i32]
+// CHECK:STDOUT:     %.loc32_21.3: type = converted %int.make_type_32.loc32_17, %.loc32_21.2 [template = i32]
+// CHECK:STDOUT:     %.loc32_21.4: type = converted %.loc32_21.1, constants.%.3 [template = constants.%.3]
+// CHECK:STDOUT:     %c.loc32_13.1: %.3 = param c, runtime_param0
+// CHECK:STDOUT:     %c.loc32_13.2: %.3 = bind_name c, %c.loc32_13.1
+// CHECK:STDOUT:     %int.make_type_32.loc32_32: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:     %.loc32_32.1: type = value_of_initializer %int.make_type_32.loc32_32 [template = i32]
+// CHECK:STDOUT:     %.loc32_32.2: type = converted %int.make_type_32.loc32_32, %.loc32_32.1 [template = i32]
+// CHECK:STDOUT:     %.loc32_35: type = struct_type {.c: i32} [template = constants.%.4]
+// CHECK:STDOUT:     %return.var.loc32: ref %.4 = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %D.decl: %D.type = fn_decl @D [template = constants.%D] {}
 // CHECK:STDOUT:   %E.decl: %E.type = fn_decl @E [template = constants.%E] {}
-// CHECK:STDOUT:   %.loc62_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc62_9.2: type = converted %.loc62_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc52_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc52_9.2: type = converted %.loc52_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %a.var: ref %.1 = var a
 // CHECK:STDOUT:   %a: ref %.1 = bind_name a, %a.var
-// CHECK:STDOUT:   %int.make_type_32.loc63: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:   %.loc63_8.1: type = value_of_initializer %int.make_type_32.loc63 [template = i32]
-// CHECK:STDOUT:   %.loc63_8.2: type = converted %int.make_type_32.loc63, %.loc63_8.1 [template = i32]
+// CHECK:STDOUT:   %int.make_type_32.loc53: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:   %.loc53_8.1: type = value_of_initializer %int.make_type_32.loc53 [template = i32]
+// CHECK:STDOUT:   %.loc53_8.2: type = converted %int.make_type_32.loc53, %.loc53_8.1 [template = i32]
 // CHECK:STDOUT:   %b.var: ref i32 = var b
-// CHECK:STDOUT:   %b.loc63: ref i32 = bind_name b, %b.var
-// CHECK:STDOUT:   %int.make_type_32.loc64: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:   %.loc64_13.1: type = value_of_initializer %int.make_type_32.loc64 [template = i32]
-// CHECK:STDOUT:   %.loc64_13.2: type = converted %int.make_type_32.loc64, %.loc64_13.1 [template = i32]
-// CHECK:STDOUT:   %.loc64_16: type = struct_type {.c: i32} [template = constants.%.4]
+// CHECK:STDOUT:   %b.loc53: ref i32 = bind_name b, %b.var
+// CHECK:STDOUT:   %int.make_type_32.loc54: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:   %.loc54_13.1: type = value_of_initializer %int.make_type_32.loc54 [template = i32]
+// CHECK:STDOUT:   %.loc54_13.2: type = converted %int.make_type_32.loc54, %.loc54_13.1 [template = i32]
+// CHECK:STDOUT:   %.loc54_16: type = struct_type {.c: i32} [template = constants.%.4]
 // CHECK:STDOUT:   %c.var: ref %.4 = var c
-// CHECK:STDOUT:   %c.loc64: ref %.4 = bind_name c, %c.var
-// CHECK:STDOUT:   %.loc65_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc65_9.2: type = converted %.loc65_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %c.loc54: ref %.4 = bind_name c, %c.var
+// CHECK:STDOUT:   %.loc55_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc55_9.2: type = converted %.loc55_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %d.var: ref %.1 = var d
 // CHECK:STDOUT:   %d: ref %.1 = bind_name d, %d.var
-// CHECK:STDOUT:   %.loc66_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc66_9.2: type = converted %.loc66_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc56_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc56_9.2: type = converted %.loc56_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %e.var: ref %.1 = var e
 // CHECK:STDOUT:   %e: ref %.1 = bind_name e, %e.var
 // CHECK:STDOUT: }
@@ -746,15 +696,15 @@ import library "extern_api";
 // CHECK:STDOUT:   %A.call: init %.1 = call %A.ref()
 // CHECK:STDOUT:   assign file.%a.var, %A.call
 // CHECK:STDOUT:   %B.ref: %B.type = name_ref B, file.%B.decl [template = constants.%B]
-// CHECK:STDOUT:   %.loc63: i32 = int_literal 1 [template = constants.%.5]
-// CHECK:STDOUT:   %B.call: init i32 = call %B.ref(%.loc63)
+// CHECK:STDOUT:   %.loc53: i32 = int_literal 1 [template = constants.%.5]
+// CHECK:STDOUT:   %B.call: init i32 = call %B.ref(%.loc53)
 // CHECK:STDOUT:   assign file.%b.var, %B.call
 // CHECK:STDOUT:   %C.ref: %C.type = name_ref C, file.%C.decl [template = constants.%C]
-// CHECK:STDOUT:   %.loc64_23: i32 = int_literal 1 [template = constants.%.5]
-// CHECK:STDOUT:   %.loc64_25: %.3 = tuple_literal (%.loc64_23)
-// CHECK:STDOUT:   %tuple: %.3 = tuple_value (%.loc64_23) [template = constants.%tuple]
-// CHECK:STDOUT:   %.loc64_21: %.3 = converted %.loc64_25, %tuple [template = constants.%tuple]
-// CHECK:STDOUT:   %C.call: init %.4 = call %C.ref(%.loc64_21)
+// CHECK:STDOUT:   %.loc54_23: i32 = int_literal 1 [template = constants.%.5]
+// CHECK:STDOUT:   %.loc54_25: %.3 = tuple_literal (%.loc54_23)
+// CHECK:STDOUT:   %tuple: %.3 = tuple_value (%.loc54_23) [template = constants.%tuple]
+// CHECK:STDOUT:   %.loc54_21: %.3 = converted %.loc54_25, %tuple [template = constants.%tuple]
+// CHECK:STDOUT:   %C.call: init %.4 = call %C.ref(%.loc54_21)
 // CHECK:STDOUT:   assign file.%c.var, %C.call
 // CHECK:STDOUT:   %D.ref: %D.type = name_ref D, file.%D.decl [template = constants.%D]
 // CHECK:STDOUT:   %D.call: init %.1 = call %D.ref()
@@ -987,27 +937,27 @@ import library "extern_api";
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %default.import = import <invalid>
-// CHECK:STDOUT:   %.loc72_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc72_9.2: type = converted %.loc72_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc52_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc52_9.2: type = converted %.loc52_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %a.var: ref %.1 = var a
 // CHECK:STDOUT:   %a: ref %.1 = bind_name a, %a.var
-// CHECK:STDOUT:   %int.make_type_32.loc73: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:   %.loc73_8.1: type = value_of_initializer %int.make_type_32.loc73 [template = i32]
-// CHECK:STDOUT:   %.loc73_8.2: type = converted %int.make_type_32.loc73, %.loc73_8.1 [template = i32]
+// CHECK:STDOUT:   %int.make_type_32.loc53: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:   %.loc53_8.1: type = value_of_initializer %int.make_type_32.loc53 [template = i32]
+// CHECK:STDOUT:   %.loc53_8.2: type = converted %int.make_type_32.loc53, %.loc53_8.1 [template = i32]
 // CHECK:STDOUT:   %b.var: ref i32 = var b
 // CHECK:STDOUT:   %b: ref i32 = bind_name b, %b.var
-// CHECK:STDOUT:   %int.make_type_32.loc74: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:   %.loc74_13.1: type = value_of_initializer %int.make_type_32.loc74 [template = i32]
-// CHECK:STDOUT:   %.loc74_13.2: type = converted %int.make_type_32.loc74, %.loc74_13.1 [template = i32]
-// CHECK:STDOUT:   %.loc74_16: type = struct_type {.c: i32} [template = constants.%.3]
+// CHECK:STDOUT:   %int.make_type_32.loc54: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:   %.loc54_13.1: type = value_of_initializer %int.make_type_32.loc54 [template = i32]
+// CHECK:STDOUT:   %.loc54_13.2: type = converted %int.make_type_32.loc54, %.loc54_13.1 [template = i32]
+// CHECK:STDOUT:   %.loc54_16: type = struct_type {.c: i32} [template = constants.%.3]
 // CHECK:STDOUT:   %c.var: ref %.3 = var c
 // CHECK:STDOUT:   %c: ref %.3 = bind_name c, %c.var
-// CHECK:STDOUT:   %.loc75_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc75_9.2: type = converted %.loc75_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc55_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc55_9.2: type = converted %.loc55_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %d.var: ref %.1 = var d
 // CHECK:STDOUT:   %d: ref %.1 = bind_name d, %d.var
-// CHECK:STDOUT:   %.loc76_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc76_9.2: type = converted %.loc76_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc56_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc56_9.2: type = converted %.loc56_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %e.var: ref %.1 = var e
 // CHECK:STDOUT:   %e: ref %.1 = bind_name e, %e.var
 // CHECK:STDOUT: }
@@ -1030,15 +980,15 @@ import library "extern_api";
 // CHECK:STDOUT:   %A.call: init %.1 = call %A.ref()
 // CHECK:STDOUT:   assign file.%a.var, %A.call
 // CHECK:STDOUT:   %B.ref: %B.type = name_ref B, imports.%import_ref.2 [template = constants.%B]
-// CHECK:STDOUT:   %.loc73: i32 = int_literal 1 [template = constants.%.2]
-// CHECK:STDOUT:   %B.call: init i32 = call %B.ref(%.loc73)
+// CHECK:STDOUT:   %.loc53: i32 = int_literal 1 [template = constants.%.2]
+// CHECK:STDOUT:   %B.call: init i32 = call %B.ref(%.loc53)
 // CHECK:STDOUT:   assign file.%b.var, %B.call
 // CHECK:STDOUT:   %C.ref: %C.type = name_ref C, imports.%import_ref.3 [template = constants.%C]
-// CHECK:STDOUT:   %.loc74_23: i32 = int_literal 1 [template = constants.%.2]
-// CHECK:STDOUT:   %.loc74_25: %.4 = tuple_literal (%.loc74_23)
-// CHECK:STDOUT:   %tuple: %.4 = tuple_value (%.loc74_23) [template = constants.%tuple]
-// CHECK:STDOUT:   %.loc74_21: %.4 = converted %.loc74_25, %tuple [template = constants.%tuple]
-// CHECK:STDOUT:   %C.call: init %.3 = call %C.ref(%.loc74_21)
+// CHECK:STDOUT:   %.loc54_23: i32 = int_literal 1 [template = constants.%.2]
+// CHECK:STDOUT:   %.loc54_25: %.4 = tuple_literal (%.loc54_23)
+// CHECK:STDOUT:   %tuple: %.4 = tuple_value (%.loc54_23) [template = constants.%tuple]
+// CHECK:STDOUT:   %.loc54_21: %.4 = converted %.loc54_25, %tuple [template = constants.%tuple]
+// CHECK:STDOUT:   %C.call: init %.3 = call %C.ref(%.loc54_21)
 // CHECK:STDOUT:   assign file.%c.var, %C.call
 // CHECK:STDOUT:   %D.ref: %D.type = name_ref D, imports.%import_ref.4 [template = constants.%D]
 // CHECK:STDOUT:   %D.call: init %.1 = call %D.ref()
@@ -1117,27 +1067,27 @@ import library "extern_api";
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %default.import = import <invalid>
-// CHECK:STDOUT:   %.loc71_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc71_9.2: type = converted %.loc71_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc51_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc51_9.2: type = converted %.loc51_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %a.var: ref %.1 = var a
 // CHECK:STDOUT:   %a: ref %.1 = bind_name a, %a.var
-// CHECK:STDOUT:   %int.make_type_32.loc72: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:   %.loc72_8.1: type = value_of_initializer %int.make_type_32.loc72 [template = i32]
-// CHECK:STDOUT:   %.loc72_8.2: type = converted %int.make_type_32.loc72, %.loc72_8.1 [template = i32]
+// CHECK:STDOUT:   %int.make_type_32.loc52: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:   %.loc52_8.1: type = value_of_initializer %int.make_type_32.loc52 [template = i32]
+// CHECK:STDOUT:   %.loc52_8.2: type = converted %int.make_type_32.loc52, %.loc52_8.1 [template = i32]
 // CHECK:STDOUT:   %b.var: ref i32 = var b
 // CHECK:STDOUT:   %b: ref i32 = bind_name b, %b.var
-// CHECK:STDOUT:   %int.make_type_32.loc73: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:   %.loc73_13.1: type = value_of_initializer %int.make_type_32.loc73 [template = i32]
-// CHECK:STDOUT:   %.loc73_13.2: type = converted %int.make_type_32.loc73, %.loc73_13.1 [template = i32]
-// CHECK:STDOUT:   %.loc73_16: type = struct_type {.c: i32} [template = constants.%.3]
+// CHECK:STDOUT:   %int.make_type_32.loc53: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:   %.loc53_13.1: type = value_of_initializer %int.make_type_32.loc53 [template = i32]
+// CHECK:STDOUT:   %.loc53_13.2: type = converted %int.make_type_32.loc53, %.loc53_13.1 [template = i32]
+// CHECK:STDOUT:   %.loc53_16: type = struct_type {.c: i32} [template = constants.%.3]
 // CHECK:STDOUT:   %c.var: ref %.3 = var c
 // CHECK:STDOUT:   %c: ref %.3 = bind_name c, %c.var
-// CHECK:STDOUT:   %.loc74_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc74_9.2: type = converted %.loc74_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc54_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc54_9.2: type = converted %.loc54_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %d.var: ref %.1 = var d
 // CHECK:STDOUT:   %d: ref %.1 = bind_name d, %d.var
-// CHECK:STDOUT:   %.loc75_9.1: %.1 = tuple_literal ()
-// CHECK:STDOUT:   %.loc75_9.2: type = converted %.loc75_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %.loc55_9.1: %.1 = tuple_literal ()
+// CHECK:STDOUT:   %.loc55_9.2: type = converted %.loc55_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %e.var: ref %.1 = var e
 // CHECK:STDOUT:   %e: ref %.1 = bind_name e, %e.var
 // CHECK:STDOUT: }
@@ -1160,15 +1110,15 @@ import library "extern_api";
 // CHECK:STDOUT:   %A.call: init %.1 = call %A.ref()
 // CHECK:STDOUT:   assign file.%a.var, %A.call
 // CHECK:STDOUT:   %B.ref: %B.type = name_ref B, imports.%import_ref.2 [template = constants.%B]
-// CHECK:STDOUT:   %.loc72: i32 = int_literal 1 [template = constants.%.2]
-// CHECK:STDOUT:   %B.call: init i32 = call %B.ref(%.loc72)
+// CHECK:STDOUT:   %.loc52: i32 = int_literal 1 [template = constants.%.2]
+// CHECK:STDOUT:   %B.call: init i32 = call %B.ref(%.loc52)
 // CHECK:STDOUT:   assign file.%b.var, %B.call
 // CHECK:STDOUT:   %C.ref: %C.type = name_ref C, imports.%import_ref.3 [template = constants.%C]
-// CHECK:STDOUT:   %.loc73_23: i32 = int_literal 1 [template = constants.%.2]
-// CHECK:STDOUT:   %.loc73_25: %.4 = tuple_literal (%.loc73_23)
-// CHECK:STDOUT:   %tuple: %.4 = tuple_value (%.loc73_23) [template = constants.%tuple]
-// CHECK:STDOUT:   %.loc73_21: %.4 = converted %.loc73_25, %tuple [template = constants.%tuple]
-// CHECK:STDOUT:   %C.call: init %.3 = call %C.ref(%.loc73_21)
+// CHECK:STDOUT:   %.loc53_23: i32 = int_literal 1 [template = constants.%.2]
+// CHECK:STDOUT:   %.loc53_25: %.4 = tuple_literal (%.loc53_23)
+// CHECK:STDOUT:   %tuple: %.4 = tuple_value (%.loc53_23) [template = constants.%tuple]
+// CHECK:STDOUT:   %.loc53_21: %.4 = converted %.loc53_25, %tuple [template = constants.%tuple]
+// CHECK:STDOUT:   %C.call: init %.3 = call %C.ref(%.loc53_21)
 // CHECK:STDOUT:   assign file.%c.var, %C.call
 // CHECK:STDOUT:   %D.ref: %D.type = name_ref D, imports.%import_ref.4 [template = constants.%D]
 // CHECK:STDOUT:   %D.call: init %.1 = call %D.ref()

toolchain/check/testdata/function/declaration/no_prelude/extern.carbon

@@ -28,7 +28,7 @@ extern fn F();
 // CHECK:STDERR: fail_redecl.carbon:[[@LINE+7]]:1: error: redeclaration of `fn F` is redundant
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -42,7 +42,7 @@ extern fn F();
 // CHECK:STDERR: fail_redecl_extern.carbon:[[@LINE+7]]:1: error: redeclaration of `fn F` is redundant
 // CHECK:STDERR: fn F();
 // CHECK:STDERR: ^~~~~~~
-// CHECK:STDERR: fail_redecl_extern.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_redecl_extern.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:

toolchain/check/testdata/function/declaration/no_prelude/extern_library.carbon

@@ -28,13 +28,11 @@ library "[[@TEST_NAME]]";
 
 import library "extern_library";
 
-// CHECK:STDERR: fail_extern_library_nonowner.carbon:[[@LINE+10]]:1: error: declaration in library "extern_library_nonowner" doesn't match `extern library` declaration
+// CHECK:STDERR: fail_extern_library_nonowner.carbon:[[@LINE+8]]:1: error: declaration in library "extern_library_nonowner" doesn't match `extern library` declaration
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR: fail_extern_library_nonowner.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "extern_library";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_library.carbon:4:1: previously declared with `extern library` here
+// CHECK:STDERR: extern_library.carbon:4:1: note: previously declared with `extern library` here
 // CHECK:STDERR: extern library "extern_library_owner" fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -46,13 +44,11 @@ library "[[@TEST_NAME]]";
 
 import library "extern_library";
 
-// CHECK:STDERR: fail_extern_library_nonextern.carbon:[[@LINE+10]]:1: error: redeclarations of `fn F` must match use of `extern`
+// CHECK:STDERR: fail_extern_library_nonextern.carbon:[[@LINE+8]]:1: error: redeclarations of `fn F` must match use of `extern`
 // CHECK:STDERR: fn F();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR: fail_extern_library_nonextern.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "extern_library";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_library.carbon:4:1: previously declared here
+// CHECK:STDERR: extern_library.carbon:4:1: note: previously declared here
 // CHECK:STDERR: extern library "extern_library_owner" fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -64,13 +60,11 @@ library "[[@TEST_NAME]]";
 
 import library "extern_library";
 
-// CHECK:STDERR: fail_extern_library_redecl.carbon:[[@LINE+10]]:1: error: declaration in library "extern_library_redecl" doesn't match `extern library` declaration
+// CHECK:STDERR: fail_extern_library_redecl.carbon:[[@LINE+8]]:1: error: declaration in library "extern_library_redecl" doesn't match `extern library` declaration
 // CHECK:STDERR: extern library "extern_library_owner" fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_extern_library_redecl.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "extern_library";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_library.carbon:4:1: previously declared with `extern library` here
+// CHECK:STDERR: extern_library.carbon:4:1: note: previously declared with `extern library` here
 // CHECK:STDERR: extern library "extern_library_owner" fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -86,16 +80,12 @@ extern library "extern_library_owner" fn F();
 
 library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_extern_library_collision.carbon:[[@LINE+13]]:1: in import
-// CHECK:STDERR: import library "extern_library";
-// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: fail_extern_library_collision.carbon:[[@LINE+9]]:1: in import
 // CHECK:STDERR: extern_library_copy.carbon:4:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: extern library "extern_library_owner" fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_extern_library_collision.carbon:[[@LINE+7]]:1: in import
-// CHECK:STDERR: import library "extern_library";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_library.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_extern_library_collision.carbon:[[@LINE+5]]:1: in import
+// CHECK:STDERR: extern_library.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: extern library "extern_library_owner" fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -142,13 +132,11 @@ library "[[@TEST_NAME]]";
 
 import library "extern_of_import";
 
-// CHECK:STDERR: fail_extern_of_import_redecl.carbon:[[@LINE+9]]:1: error: redeclarations of `fn F` must match use of `extern`
+// CHECK:STDERR: fail_extern_of_import_redecl.carbon:[[@LINE+7]]:1: error: redeclarations of `fn F` must match use of `extern`
 // CHECK:STDERR: extern library "extern_of_import" fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_extern_of_import_redecl.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "extern_of_import";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_of_import.carbon:4:1: previously declared here
+// CHECK:STDERR: extern_of_import.carbon:4:1: note: previously declared here
 // CHECK:STDERR: fn F();
 // CHECK:STDERR: ^~~~~~~
 extern library "extern_of_import" fn F();

toolchain/check/testdata/function/declaration/no_prelude/extern_library_for_default.carbon

@@ -28,13 +28,11 @@ package Foo library "[[@TEST_NAME]]";
 
 import library default;
 
-// CHECK:STDERR: fail_wrong_library.carbon:[[@LINE+9]]:1: error: declaration in library "wrong_library" doesn't match `extern library` declaration
+// CHECK:STDERR: fail_wrong_library.carbon:[[@LINE+7]]:1: error: declaration in library "wrong_library" doesn't match `extern library` declaration
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR: fail_wrong_library.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library default;
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: default.carbon:4:1: previously declared with `extern library` here
+// CHECK:STDERR: default.carbon:4:1: note: previously declared with `extern library` here
 // CHECK:STDERR: extern library "expected" fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 extern fn F();

toolchain/check/testdata/function/declaration/no_prelude/extern_library_from_default.carbon

@@ -26,13 +26,11 @@ library "[[@TEST_NAME]]";
 
 import library "extern_library";
 
-// CHECK:STDERR: fail_wrong_library.carbon:[[@LINE+9]]:1: error: declaration in library "wrong_library" doesn't match `extern library` declaration
+// CHECK:STDERR: fail_wrong_library.carbon:[[@LINE+7]]:1: error: declaration in library "wrong_library" doesn't match `extern library` declaration
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR: fail_wrong_library.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "extern_library";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern_library.carbon:4:1: previously declared with `extern library` here
+// CHECK:STDERR: extern_library.carbon:4:1: note: previously declared with `extern library` here
 // CHECK:STDERR: extern library default fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 extern fn F();

toolchain/check/testdata/function/declaration/no_prelude/fail_import_incomplete_return.carbon

@@ -24,10 +24,10 @@ fn Call() {
   // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE+10]]:3: error: function returns incomplete type `C`
   // CHECK:STDERR:   ReturnCUsed();
   // CHECK:STDERR:   ^~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE-12]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE-12]]:1: note: class was forward declared here
   // CHECK:STDERR: class C;
   // CHECK:STDERR: ^~~~~~~~
-  // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE-11]]:18: return type declared here
+  // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE-11]]:18: note: return type declared here
   // CHECK:STDERR: fn ReturnCUsed() -> C;
   // CHECK:STDERR:                  ^~~~
   // CHECK:STDERR:
@@ -35,10 +35,10 @@ fn Call() {
   // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE+10]]:3: error: function returns incomplete type `D`
   // CHECK:STDERR:   ReturnDUsed();
   // CHECK:STDERR:   ^~~~~~~~~~~
-  // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE-22]]:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE-22]]:1: note: class was forward declared here
   // CHECK:STDERR: class D;
   // CHECK:STDERR: ^~~~~~~~
-  // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE-20]]:18: return type declared here
+  // CHECK:STDERR: fail_incomplete_return.carbon:[[@LINE-20]]:18: note: return type declared here
   // CHECK:STDERR: fn ReturnDUsed() -> D;
   // CHECK:STDERR:                  ^~~~
   // CHECK:STDERR:
@@ -54,36 +54,28 @@ library "[[@TEST_NAME]]";
 import library "incomplete_return";
 
 fn CallFAndGIncomplete() {
-  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE+16]]:3: error: function returns incomplete type `C`
+  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE+12]]:3: error: function returns incomplete type `C`
   // CHECK:STDERR:   ReturnCUnused();
   // CHECK:STDERR:   ^~~~~~~~~~~~~
   // CHECK:STDERR: fail_use_imported.carbon:[[@LINE-6]]:1: in import
-  // CHECK:STDERR: import library "incomplete_return";
-  // CHECK:STDERR: ^~~~~~
-  // CHECK:STDERR: fail_incomplete_return.carbon:4:1: class was forward declared here
+  // CHECK:STDERR: fail_incomplete_return.carbon:4:1: note: class was forward declared here
   // CHECK:STDERR: class C;
   // CHECK:STDERR: ^~~~~~~~
-  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE-12]]:1: in import
-  // CHECK:STDERR: import library "incomplete_return";
-  // CHECK:STDERR: ^~~~~~
-  // CHECK:STDERR: fail_incomplete_return.carbon:7:20: return type declared here
+  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE-10]]:1: in import
+  // CHECK:STDERR: fail_incomplete_return.carbon:7:20: note: return type declared here
   // CHECK:STDERR: fn ReturnCUnused() -> C;
   // CHECK:STDERR:                    ^~~~
   // CHECK:STDERR:
   ReturnCUnused();
-  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE+15]]:3: error: function returns incomplete type `C`
+  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE+11]]:3: error: function returns incomplete type `C`
   // CHECK:STDERR:   ReturnCUsed();
   // CHECK:STDERR:   ^~~~~~~~~~~
-  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE-23]]:1: in import
-  // CHECK:STDERR: import library "incomplete_return";
-  // CHECK:STDERR: ^~~~~~
-  // CHECK:STDERR: fail_incomplete_return.carbon:4:1: class was forward declared here
+  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE-19]]:1: in import
+  // CHECK:STDERR: fail_incomplete_return.carbon:4:1: note: class was forward declared here
   // CHECK:STDERR: class C;
   // CHECK:STDERR: ^~~~~~~~
-  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE-29]]:1: in import
-  // CHECK:STDERR: import library "incomplete_return";
-  // CHECK:STDERR: ^~~~~~
-  // CHECK:STDERR: fail_incomplete_return.carbon:8:18: return type declared here
+  // CHECK:STDERR: fail_use_imported.carbon:[[@LINE-23]]:1: in import
+  // CHECK:STDERR: fail_incomplete_return.carbon:8:18: note: return type declared here
   // CHECK:STDERR: fn ReturnCUsed() -> C;
   // CHECK:STDERR:                  ^~~~
   ReturnCUsed();
@@ -230,13 +222,13 @@ fn CallFAndGIncomplete() {
 // CHECK:STDOUT:   %ReturnCUsed.ref: %ReturnCUsed.type = name_ref ReturnCUsed, imports.%import_ref.4 [template = constants.%ReturnCUsed]
 // CHECK:STDOUT:   %ReturnCUsed.call: init <error> = call %ReturnCUsed.ref()
 // CHECK:STDOUT:   %ReturnDUnused.ref: %ReturnDUnused.type = name_ref ReturnDUnused, imports.%import_ref.5 [template = constants.%ReturnDUnused]
-// CHECK:STDOUT:   %.loc40_16.1: ref %D = temporary_storage
-// CHECK:STDOUT:   %ReturnDUnused.call: init %D = call %ReturnDUnused.ref() to %.loc40_16.1
-// CHECK:STDOUT:   %.loc40_16.2: ref %D = temporary %.loc40_16.1, %ReturnDUnused.call
+// CHECK:STDOUT:   %.loc32_16.1: ref %D = temporary_storage
+// CHECK:STDOUT:   %ReturnDUnused.call: init %D = call %ReturnDUnused.ref() to %.loc32_16.1
+// CHECK:STDOUT:   %.loc32_16.2: ref %D = temporary %.loc32_16.1, %ReturnDUnused.call
 // CHECK:STDOUT:   %ReturnDUsed.ref: %ReturnDUsed.type = name_ref ReturnDUsed, imports.%import_ref.6 [template = constants.%ReturnDUsed]
-// CHECK:STDOUT:   %.loc41_14.1: ref %D = temporary_storage
-// CHECK:STDOUT:   %ReturnDUsed.call: init %D = call %ReturnDUsed.ref() to %.loc41_14.1
-// CHECK:STDOUT:   %.loc41_14.2: ref %D = temporary %.loc41_14.1, %ReturnDUsed.call
+// CHECK:STDOUT:   %.loc33_14.1: ref %D = temporary_storage
+// CHECK:STDOUT:   %ReturnDUsed.call: init %D = call %ReturnDUsed.ref() to %.loc33_14.1
+// CHECK:STDOUT:   %.loc33_14.2: ref %D = temporary %.loc33_14.1, %ReturnDUsed.call
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/function/declaration/no_prelude/fail_modifiers.carbon

@@ -15,7 +15,7 @@
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:9: error: `protected` must appear before `default`
 // CHECK:STDERR: default protected fn WrongOrder();
 // CHECK:STDERR:         ^~~~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `default` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `default` previously appeared here
 // CHECK:STDERR: default protected fn WrongOrder();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -28,7 +28,7 @@ default protected fn WrongOrder();
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:9: error: `virtual` repeated on declaration
 // CHECK:STDERR: virtual virtual fn DuplicateVirtual() {}
 // CHECK:STDERR:         ^~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `virtual` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `virtual` previously appeared here
 // CHECK:STDERR: virtual virtual fn DuplicateVirtual() {}
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -37,7 +37,7 @@ virtual virtual fn DuplicateVirtual() {}
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:9: error: `protected` not allowed on declaration with `private`
 // CHECK:STDERR: private protected fn TwoAccess();
 // CHECK:STDERR:         ^~~~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `private` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `private` previously appeared here
 // CHECK:STDERR: private protected fn TwoAccess();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -50,7 +50,7 @@ private protected fn TwoAccess();
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:10: error: `virtual` not allowed on declaration with `abstract`
 // CHECK:STDERR: abstract virtual fn ModifiersConflict() {}
 // CHECK:STDERR:          ^~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `abstract` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `abstract` previously appeared here
 // CHECK:STDERR: abstract virtual fn ModifiersConflict() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -69,14 +69,14 @@ base fn InvalidModifier();
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+14]]:9: error: `final` not allowed on declaration with `default`
 // CHECK:STDERR: default final virtual fn ModifiersConflict2() {}
 // CHECK:STDERR:         ^~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+11]]:1: `default` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+11]]:1: note: `default` previously appeared here
 // CHECK:STDERR: default final virtual fn ModifiersConflict2() {}
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:15: error: `virtual` not allowed on declaration with `default`
 // CHECK:STDERR: default final virtual fn ModifiersConflict2() {}
 // CHECK:STDERR:               ^~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `default` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `default` previously appeared here
 // CHECK:STDERR: default final virtual fn ModifiersConflict2() {}
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -85,7 +85,7 @@ default final virtual fn ModifiersConflict2() {}
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+6]]:8: error: `private` must appear before `extern`
 // CHECK:STDERR: extern private fn ExternOrderAndConflict() {}
 // CHECK:STDERR:        ^~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+3]]:1: `extern` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+3]]:1: note: `extern` previously appeared here
 // CHECK:STDERR: extern private fn ExternOrderAndConflict() {}
 // CHECK:STDERR: ^~~~~~
 extern private fn ExternOrderAndConflict() {}

toolchain/check/testdata/function/declaration/no_prelude/fail_redecl.carbon

@@ -12,7 +12,7 @@ fn A();
 // CHECK:STDERR: fail_redecl.carbon:[[@LINE+7]]:1: error: redeclaration of `fn A` is redundant
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
-// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -22,7 +22,7 @@ fn B(x: ());
 // CHECK:STDERR: fail_redecl.carbon:[[@LINE+7]]:1: error: redeclaration of `fn B` is redundant
 // CHECK:STDERR: fn B(x: ());
 // CHECK:STDERR: ^~~~~~~~~~~~
-// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: fn B(x: ());
 // CHECK:STDERR: ^~~~~~~~~~~~
 // CHECK:STDERR:
@@ -32,7 +32,7 @@ fn C();
 // CHECK:STDERR: fail_redecl.carbon:[[@LINE+7]]:1: error: redeclaration differs because of parameter count of 1
 // CHECK:STDERR: fn C(x: ());
 // CHECK:STDERR: ^~~~~~~~~~~~
-// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: previously declared with parameter count of 0
+// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: note: previously declared with parameter count of 0
 // CHECK:STDERR: fn C();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -42,7 +42,7 @@ fn D() {}
 // CHECK:STDERR: fail_redecl.carbon:[[@LINE+7]]:1: error: redeclaration of `fn D` is redundant
 // CHECK:STDERR: fn D();
 // CHECK:STDERR: ^~~~~~~
-// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: fn D() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -52,7 +52,7 @@ fn E() {}
 // CHECK:STDERR: fail_redecl.carbon:[[@LINE+6]]:1: error: redefinition of `fn E`
 // CHECK:STDERR: fn E() {}
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: previously defined here
+// CHECK:STDERR: fail_redecl.carbon:[[@LINE-4]]:1: note: previously defined here
 // CHECK:STDERR: fn E() {}
 // CHECK:STDERR: ^~~~~~~~
 fn E() {}

toolchain/check/testdata/function/declaration/no_prelude/implicit_import.carbon

@@ -30,13 +30,11 @@ extern fn A();
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_extern_api.impl.carbon:[[@LINE+14]]:1: error: redeclarations of `fn A` must match use of `extern`
+// CHECK:STDERR: fail_extern_api.impl.carbon:[[@LINE+12]]:1: error: redeclarations of `fn A` must match use of `extern`
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR: fail_extern_api.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "extern_api";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: extern_api.carbon:4:1: previously declared here
+// CHECK:STDERR: extern_api.carbon:4:1: note: previously declared here
 // CHECK:STDERR: extern fn A();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -56,13 +54,11 @@ fn A();
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_extern_impl.impl.carbon:[[@LINE+9]]:1: error: redeclarations of `fn A` must match use of `extern`
+// CHECK:STDERR: fail_extern_impl.impl.carbon:[[@LINE+7]]:1: error: redeclarations of `fn A` must match use of `extern`
 // CHECK:STDERR: extern fn A();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR: fail_extern_impl.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "extern_impl";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: extern_impl.carbon:4:1: previously declared here
+// CHECK:STDERR: extern_impl.carbon:4:1: note: previously declared here
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
 extern fn A();

toolchain/check/testdata/function/definition/import.carbon

@@ -47,24 +47,20 @@ library "[[@TEST_NAME]]";
 
 import library "fns";
 
-// CHECK:STDERR: fail_def_ownership.carbon:[[@LINE+10]]:1: error: redeclaration of `fn A` is redundant
+// CHECK:STDERR: fail_def_ownership.carbon:[[@LINE+8]]:1: error: redeclaration of `fn A` is redundant
 // CHECK:STDERR: fn A() {};
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR: fail_def_ownership.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "fns";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: fns.carbon:4:1: previously declared here
+// CHECK:STDERR: fns.carbon:4:1: note: previously declared here
 // CHECK:STDERR: fn A() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
 fn A() {};
-// CHECK:STDERR: fail_def_ownership.carbon:[[@LINE+10]]:1: error: redeclaration of `fn B` is redundant
+// CHECK:STDERR: fail_def_ownership.carbon:[[@LINE+8]]:1: error: redeclaration of `fn B` is redundant
 // CHECK:STDERR: fn B(b: i32) -> i32;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_def_ownership.carbon:[[@LINE-16]]:1: in import
-// CHECK:STDERR: import library "fns";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: fns.carbon:5:1: previously declared here
+// CHECK:STDERR: fail_def_ownership.carbon:[[@LINE-14]]:1: in import
+// CHECK:STDERR: fns.carbon:5:1: note: previously declared here
 // CHECK:STDERR: fn B(b: i32) -> i32 { return b; }
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -76,25 +72,21 @@ library "[[@TEST_NAME]]";
 
 import library "extern";
 
-// CHECK:STDERR: fail_redecl_then_def.carbon:[[@LINE+10]]:1: error: redeclarations of `fn A` must match use of `extern`
+// CHECK:STDERR: fail_redecl_then_def.carbon:[[@LINE+8]]:1: error: redeclarations of `fn A` must match use of `extern`
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR: fail_redecl_then_def.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "extern";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern.carbon:4:1: previously declared here
+// CHECK:STDERR: extern.carbon:4:1: note: previously declared here
 // CHECK:STDERR: extern fn A();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
 fn A();
 
-// CHECK:STDERR: fail_redecl_then_def.carbon:[[@LINE+10]]:1: error: redeclarations of `fn A` must match use of `extern`
+// CHECK:STDERR: fail_redecl_then_def.carbon:[[@LINE+8]]:1: error: redeclarations of `fn A` must match use of `extern`
 // CHECK:STDERR: fn A() {}
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_redecl_then_def.carbon:[[@LINE-17]]:1: in import
-// CHECK:STDERR: import library "extern";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: extern.carbon:4:1: previously declared here
+// CHECK:STDERR: fail_redecl_then_def.carbon:[[@LINE-15]]:1: in import
+// CHECK:STDERR: extern.carbon:4:1: note: previously declared here
 // CHECK:STDERR: extern fn A();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -106,13 +98,11 @@ library "[[@TEST_NAME]]";
 
 import library "fns";
 
-// CHECK:STDERR: fail_mix_extern_decl.carbon:[[@LINE+9]]:1: error: redeclarations of `fn D` must match use of `extern`
+// CHECK:STDERR: fail_mix_extern_decl.carbon:[[@LINE+7]]:1: error: redeclarations of `fn D` must match use of `extern`
 // CHECK:STDERR: extern fn D();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR: fail_mix_extern_decl.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "fns";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: fns.carbon:7:1: previously declared here
+// CHECK:STDERR: fns.carbon:7:1: note: previously declared here
 // CHECK:STDERR: fn D();
 // CHECK:STDERR: ^~~~~~~
 extern fn D();
@@ -387,14 +377,14 @@ fn D() {}
 // CHECK:STDOUT:   %default.import = import <invalid>
 // CHECK:STDOUT:   %A.decl: %A.type = fn_decl @A [template = constants.%A] {}
 // CHECK:STDOUT:   %B.decl: %B.type = fn_decl @B [template = constants.%B] {
-// CHECK:STDOUT:     %int.make_type_32.loc27_9: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:     %.loc27_9.1: type = value_of_initializer %int.make_type_32.loc27_9 [template = i32]
-// CHECK:STDOUT:     %.loc27_9.2: type = converted %int.make_type_32.loc27_9, %.loc27_9.1 [template = i32]
-// CHECK:STDOUT:     %b.loc27_6.1: i32 = param b, runtime_param0
-// CHECK:STDOUT:     %b.loc27_6.2: i32 = bind_name b, %b.loc27_6.1
-// CHECK:STDOUT:     %int.make_type_32.loc27_17: init type = call constants.%Int32() [template = i32]
-// CHECK:STDOUT:     %.loc27_17.1: type = value_of_initializer %int.make_type_32.loc27_17 [template = i32]
-// CHECK:STDOUT:     %.loc27_17.2: type = converted %int.make_type_32.loc27_17, %.loc27_17.1 [template = i32]
+// CHECK:STDOUT:     %int.make_type_32.loc23_9: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:     %.loc23_9.1: type = value_of_initializer %int.make_type_32.loc23_9 [template = i32]
+// CHECK:STDOUT:     %.loc23_9.2: type = converted %int.make_type_32.loc23_9, %.loc23_9.1 [template = i32]
+// CHECK:STDOUT:     %b.loc23_6.1: i32 = param b, runtime_param0
+// CHECK:STDOUT:     %b.loc23_6.2: i32 = bind_name b, %b.loc23_6.1
+// CHECK:STDOUT:     %int.make_type_32.loc23_17: init type = call constants.%Int32() [template = i32]
+// CHECK:STDOUT:     %.loc23_17.1: type = value_of_initializer %int.make_type_32.loc23_17 [template = i32]
+// CHECK:STDOUT:     %.loc23_17.2: type = converted %int.make_type_32.loc23_17, %.loc23_17.1 [template = i32]
 // CHECK:STDOUT:     %return.var: ref i32 = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
@@ -432,13 +422,13 @@ fn D() {}
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
-// CHECK:STDOUT:     .A = %A.decl.loc16
+// CHECK:STDOUT:     .A = %A.decl.loc14
 // CHECK:STDOUT:     .Core = imports.%Core
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %default.import = import <invalid>
-// CHECK:STDOUT:   %A.decl.loc16: %A.type = fn_decl @A [template = constants.%A] {}
-// CHECK:STDOUT:   %A.decl.loc28: %A.type = fn_decl @A [template = constants.%A] {}
+// CHECK:STDOUT:   %A.decl.loc14: %A.type = fn_decl @A [template = constants.%A] {}
+// CHECK:STDOUT:   %A.decl.loc24: %A.type = fn_decl @A [template = constants.%A] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @A() {
@@ -476,13 +466,13 @@ fn D() {}
 // CHECK:STDOUT:     .A = imports.%import_ref.1
 // CHECK:STDOUT:     .B = imports.%import_ref.2
 // CHECK:STDOUT:     .C = imports.%import_ref.3
-// CHECK:STDOUT:     .D = %D.decl.loc15
+// CHECK:STDOUT:     .D = %D.decl.loc13
 // CHECK:STDOUT:     .Core = imports.%Core
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %default.import = import <invalid>
+// CHECK:STDOUT:   %D.decl.loc13: %D.type = fn_decl @D [template = constants.%D] {}
 // CHECK:STDOUT:   %D.decl.loc15: %D.type = fn_decl @D [template = constants.%D] {}
-// CHECK:STDOUT:   %D.decl.loc17: %D.type = fn_decl @D [template = constants.%D] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @D() {

toolchain/check/testdata/function/definition/no_prelude/extern.carbon

@@ -41,7 +41,7 @@ extern fn F();
 // CHECK:STDERR: fail_def_extern_mismatch.carbon:[[@LINE+7]]:1: error: redeclarations of `fn F` must match use of `extern`
 // CHECK:STDERR: fn F() {}
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_def_extern_mismatch.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_def_extern_mismatch.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -55,7 +55,7 @@ fn F();
 // CHECK:STDERR: fail_def_extern_mismatch_reverse.carbon:[[@LINE+7]]:1: error: redeclarations of `fn F` must match use of `extern`
 // CHECK:STDERR: extern fn F() {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_def_extern_mismatch_reverse.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_def_extern_mismatch_reverse.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: fn F();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -69,7 +69,7 @@ extern fn F();
 // CHECK:STDERR: fail_extern_diag_suppressed.carbon:[[@LINE+7]]:1: error: redeclaration of `fn F` is redundant
 // CHECK:STDERR: fn F();
 // CHECK:STDERR: ^~~~~~~
-// CHECK:STDERR: fail_extern_diag_suppressed.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_extern_diag_suppressed.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -77,7 +77,7 @@ fn F();
 // CHECK:STDERR: fail_extern_diag_suppressed.carbon:[[@LINE+7]]:1: error: redeclarations of `fn F` must match use of `extern`
 // CHECK:STDERR: fn F() {}
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_extern_diag_suppressed.carbon:[[@LINE-12]]:1: previously declared here
+// CHECK:STDERR: fail_extern_diag_suppressed.carbon:[[@LINE-12]]:1: note: previously declared here
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -91,7 +91,7 @@ fn F() {}
 // CHECK:STDERR: fail_extern_decl_after_def.carbon:[[@LINE+7]]:1: error: redeclaration of `fn F` is redundant
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_extern_decl_after_def.carbon:[[@LINE-4]]:1: previously declared here
+// CHECK:STDERR: fail_extern_decl_after_def.carbon:[[@LINE-4]]:1: note: previously declared here
 // CHECK:STDERR: fn F() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:

toolchain/check/testdata/function/definition/no_prelude/extern_library.carbon

@@ -54,13 +54,11 @@ extern fn F();
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_two_file_impl_mismatch.impl.carbon:[[@LINE+10]]:1: error: redeclarations of `fn F` must match use of `extern`
+// CHECK:STDERR: fail_two_file_impl_mismatch.impl.carbon:[[@LINE+8]]:1: error: redeclarations of `fn F` must match use of `extern`
 // CHECK:STDERR: fn F() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR: fail_two_file_impl_mismatch.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "two_file_impl_mismatch";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: two_file_impl_mismatch.carbon:4:1: previously declared here
+// CHECK:STDERR: two_file_impl_mismatch.carbon:4:1: note: previously declared here
 // CHECK:STDERR: extern fn F();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:

toolchain/check/testdata/function/definition/no_prelude/fail_decl_param_mismatch.carbon

@@ -12,7 +12,7 @@ fn F();
 // CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE+7]]:1: error: redeclaration differs because of parameter count of 1
 // CHECK:STDERR: fn F(x: ()) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~
-// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: previously declared with parameter count of 0
+// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: note: previously declared with parameter count of 0
 // CHECK:STDERR: fn F();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -22,7 +22,7 @@ fn G(x: ());
 // CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE+7]]:1: error: redeclaration differs because of parameter count of 0
 // CHECK:STDERR: fn G() {}
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: previously declared with parameter count of 1
+// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: note: previously declared with parameter count of 1
 // CHECK:STDERR: fn G(x: ());
 // CHECK:STDERR: ^~~~~~~~~~~~
 // CHECK:STDERR:
@@ -39,7 +39,7 @@ fn I();
 // CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE+7]]:1: error: function redeclaration differs because return type is `()`
 // CHECK:STDERR: fn I() -> () { return (); }
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: previously declared with no return type
+// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: note: previously declared with no return type
 // CHECK:STDERR: fn I();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -49,7 +49,7 @@ fn J() -> ();
 // CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE+7]]:1: error: function redeclaration differs because no return type is provided
 // CHECK:STDERR: fn J() {}
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: previously declared with return type `()`
+// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: note: previously declared with return type `()`
 // CHECK:STDERR: fn J() -> ();
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -59,7 +59,7 @@ fn K() -> ();
 // CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE+6]]:1: error: function redeclaration differs because return type is `{}`
 // CHECK:STDERR: fn K() -> {} { return {}; }
 // CHECK:STDERR: ^~~~~~~~~~~~~~
-// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: previously declared with return type `()`
+// CHECK:STDERR: fail_decl_param_mismatch.carbon:[[@LINE-4]]:1: note: previously declared with return type `()`
 // CHECK:STDERR: fn K() -> ();
 // CHECK:STDERR: ^~~~~~~~~~~~~
 fn K() -> {} { return {}; }

toolchain/check/testdata/function/definition/no_prelude/fail_redef.carbon

@@ -12,7 +12,7 @@ fn F() {}
 // CHECK:STDERR: fail_redef.carbon:[[@LINE+6]]:1: error: redefinition of `fn F`
 // CHECK:STDERR: fn F() {}
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_redef.carbon:[[@LINE-4]]:1: previously defined here
+// CHECK:STDERR: fail_redef.carbon:[[@LINE-4]]:1: note: previously defined here
 // CHECK:STDERR: fn F() {}
 // CHECK:STDERR: ^~~~~~~~
 fn F() {}

toolchain/check/testdata/function/definition/no_prelude/implicit_import.carbon

@@ -30,13 +30,11 @@ extern fn A();
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_extern_api.impl.carbon:[[@LINE+10]]:1: error: redeclarations of `fn A` must match use of `extern`
+// CHECK:STDERR: fail_extern_api.impl.carbon:[[@LINE+8]]:1: error: redeclarations of `fn A` must match use of `extern`
 // CHECK:STDERR: fn A() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR: fail_extern_api.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "extern_api";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: extern_api.carbon:4:1: previously declared here
+// CHECK:STDERR: extern_api.carbon:4:1: note: previously declared here
 // CHECK:STDERR: extern fn A();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -52,13 +50,11 @@ fn A();
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_extern_impl.impl.carbon:[[@LINE+10]]:1: error: redeclarations of `fn A` must match use of `extern`
+// CHECK:STDERR: fail_extern_impl.impl.carbon:[[@LINE+8]]:1: error: redeclarations of `fn A` must match use of `extern`
 // CHECK:STDERR: extern fn A() {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_extern_impl.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "extern_impl";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: extern_impl.carbon:4:1: previously declared here
+// CHECK:STDERR: extern_impl.carbon:4:1: note: previously declared here
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -74,13 +70,11 @@ fn A() {}
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_redecl_after_def.impl.carbon:[[@LINE+10]]:1: error: redeclaration of `fn A` is redundant
+// CHECK:STDERR: fail_redecl_after_def.impl.carbon:[[@LINE+8]]:1: error: redeclaration of `fn A` is redundant
 // CHECK:STDERR: fn A();
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR: fail_redecl_after_def.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "redecl_after_def";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: redecl_after_def.carbon:4:1: previously declared here
+// CHECK:STDERR: redecl_after_def.carbon:4:1: note: previously declared here
 // CHECK:STDERR: fn A() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -96,13 +90,11 @@ fn A() {}
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_redef_after_def.impl.carbon:[[@LINE+10]]:1: error: redefinition of `fn A`
+// CHECK:STDERR: fail_redef_after_def.impl.carbon:[[@LINE+8]]:1: error: redefinition of `fn A`
 // CHECK:STDERR: fn A() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR: fail_redef_after_def.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "redef_after_def";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: redef_after_def.carbon:4:1: previously defined here
+// CHECK:STDERR: redef_after_def.carbon:4:1: note: previously defined here
 // CHECK:STDERR: fn A() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR:
@@ -119,13 +111,11 @@ alias B = A;
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_def_alias.impl.carbon:[[@LINE+9]]:1: error: duplicate name being declared in the same scope
+// CHECK:STDERR: fail_def_alias.impl.carbon:[[@LINE+7]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn B() {}
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR: fail_def_alias.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "def_alias";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: def_alias.carbon:5:7: name is previously declared here
+// CHECK:STDERR: def_alias.carbon:5:7: note: name is previously declared here
 // CHECK:STDERR: alias B = A;
 // CHECK:STDERR:       ^
 fn B() {}

toolchain/check/testdata/function/definition/no_prelude/syntactic_merge.carbon

@@ -40,7 +40,7 @@ fn Foo(a: C);
 // CHECK:STDERR: fail_parens.carbon:[[@LINE+7]]:11: error: redeclaration syntax differs here
 // CHECK:STDERR: fn Foo(a: (C)) {}
 // CHECK:STDERR:           ^
-// CHECK:STDERR: fail_parens.carbon:[[@LINE-4]]:11: comparing with previous declaration here
+// CHECK:STDERR: fail_parens.carbon:[[@LINE-4]]:11: note: comparing with previous declaration here
 // CHECK:STDERR: fn Foo(a: C);
 // CHECK:STDERR:           ^
 // CHECK:STDERR:
@@ -83,7 +83,7 @@ fn Foo(a: C);
 // CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE+7]]:8: error: redeclaration differs at parameter 1
 // CHECK:STDERR: fn Foo(b: D) {}
 // CHECK:STDERR:        ^
-// CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE-4]]:8: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE-4]]:8: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: fn Foo(a: C);
 // CHECK:STDERR:        ^
 // CHECK:STDERR:
@@ -100,7 +100,7 @@ fn Foo(a: C);
 // CHECK:STDERR: fail_alias.carbon:[[@LINE+7]]:11: error: redeclaration syntax differs here
 // CHECK:STDERR: fn Foo(a: D) {}
 // CHECK:STDERR:           ^
-// CHECK:STDERR: fail_alias.carbon:[[@LINE-4]]:11: comparing with previous declaration here
+// CHECK:STDERR: fail_alias.carbon:[[@LINE-4]]:11: note: comparing with previous declaration here
 // CHECK:STDERR: fn Foo(a: C);
 // CHECK:STDERR:           ^
 // CHECK:STDERR:
@@ -117,7 +117,7 @@ fn Foo[a: C]();
 // CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE+7]]:11: error: redeclaration syntax differs here
 // CHECK:STDERR: fn Foo[a: D]() {}
 // CHECK:STDERR:           ^
-// CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE-4]]:11: comparing with previous declaration here
+// CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE-4]]:11: note: comparing with previous declaration here
 // CHECK:STDERR: fn Foo[a: C]();
 // CHECK:STDERR:           ^
 // CHECK:STDERR:
@@ -163,7 +163,7 @@ fn Foo(a: const C);
 // CHECK:STDERR: fail_repeat_const.carbon:[[@LINE+6]]:17: error: redeclaration syntax differs here
 // CHECK:STDERR: fn Foo(a: const (const C)) {}
 // CHECK:STDERR:                 ^
-// CHECK:STDERR: fail_repeat_const.carbon:[[@LINE-8]]:17: comparing with previous declaration here
+// CHECK:STDERR: fail_repeat_const.carbon:[[@LINE-8]]:17: note: comparing with previous declaration here
 // CHECK:STDERR: fn Foo(a: const C);
 // CHECK:STDERR:                 ^
 fn Foo(a: const (const C)) {}

toolchain/check/testdata/function/generic/deduce.carbon

@@ -35,7 +35,7 @@ fn CallExplicitAndAlsoDeduced(n: i32) -> i32* {
   // CHECK:STDERR: fail_todo_explicit_vs_deduced.carbon:[[@LINE+7]]:10: error: inconsistent deductions for value of generic parameter `T`
   // CHECK:STDERR:   return ExplicitAndAlsoDeduced(A, {});
   // CHECK:STDERR:          ^~~~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_todo_explicit_vs_deduced.carbon:[[@LINE-7]]:1: while deducing parameters of generic declared here
+  // CHECK:STDERR: fail_todo_explicit_vs_deduced.carbon:[[@LINE-7]]:1: note: while deducing parameters of generic declared here
   // CHECK:STDERR: fn ExplicitAndAlsoDeduced(T:! type, x: T) -> T*;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -62,7 +62,7 @@ fn CallTupleParam() {
   // CHECK:STDERR: fail_todo_deduce_nested.carbon:[[@LINE+7]]:3: error: cannot deduce value for generic parameter `T`
   // CHECK:STDERR:   TupleParam((1, 2));
   // CHECK:STDERR:   ^~~~~~~~~~~
-  // CHECK:STDERR: fail_todo_deduce_nested.carbon:[[@LINE-6]]:1: while deducing parameters of generic declared here
+  // CHECK:STDERR: fail_todo_deduce_nested.carbon:[[@LINE-6]]:1: note: while deducing parameters of generic declared here
   // CHECK:STDERR: fn TupleParam[T:! type](x: (T, i32));
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -75,7 +75,7 @@ fn CallStructParam() {
   // CHECK:STDERR: fail_todo_deduce_nested.carbon:[[@LINE+7]]:3: error: cannot deduce value for generic parameter `T`
   // CHECK:STDERR:   StructParam({.a = 1, .b = 2});
   // CHECK:STDERR:   ^~~~~~~~~~~~
-  // CHECK:STDERR: fail_todo_deduce_nested.carbon:[[@LINE-6]]:1: while deducing parameters of generic declared here
+  // CHECK:STDERR: fail_todo_deduce_nested.carbon:[[@LINE-6]]:1: note: while deducing parameters of generic declared here
   // CHECK:STDERR: fn StructParam[T:! type](x: {.a: T, .b: i32});
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -94,7 +94,7 @@ fn CallImplicitNotDeducible() {
   // CHECK:STDERR: fail_deduce_incomplete.carbon:[[@LINE+7]]:3: error: cannot deduce value for generic parameter `U`
   // CHECK:STDERR:   ImplicitNotDeducible(42);
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_deduce_incomplete.carbon:[[@LINE-6]]:1: while deducing parameters of generic declared here
+  // CHECK:STDERR: fail_deduce_incomplete.carbon:[[@LINE-6]]:1: note: while deducing parameters of generic declared here
   // CHECK:STDERR: fn ImplicitNotDeducible[T:! type, U:! type](x: T) -> U;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -111,7 +111,7 @@ fn CallImplicitNotDeducible() {
   // CHECK:STDERR: fail_deduce_inconsistent.carbon:[[@LINE+6]]:3: error: inconsistent deductions for value of generic parameter `T`
   // CHECK:STDERR:   ImplicitNotDeducible(42, {.x = 12});
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_deduce_inconsistent.carbon:[[@LINE-6]]:1: while deducing parameters of generic declared here
+  // CHECK:STDERR: fail_deduce_inconsistent.carbon:[[@LINE-6]]:1: note: while deducing parameters of generic declared here
   // CHECK:STDERR: fn ImplicitNotDeducible[T:! type](x: T, y: T) -> T;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   ImplicitNotDeducible(42, {.x = 12});

toolchain/check/testdata/function/generic/redeclare.carbon

@@ -27,7 +27,7 @@ fn F(T:! type, U:! type) -> T*;
 // CHECK:STDERR: fail_different_return_type.carbon:[[@LINE+7]]:1: error: function redeclaration differs because return type is `U*`
 // CHECK:STDERR: fn F(T:! type, U:! type) -> U* {
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_different_return_type.carbon:[[@LINE-5]]:1: previously declared with return type `T*`
+// CHECK:STDERR: fail_different_return_type.carbon:[[@LINE-5]]:1: note: previously declared with return type `T*`
 // CHECK:STDERR: fn F(T:! type, U:! type) -> T*;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -35,7 +35,7 @@ fn F(T:! type, U:! type) -> U* {
   // CHECK:STDERR: fail_different_return_type.carbon:[[@LINE+7]]:10: error: 1 argument(s) passed to function expecting 2 argument(s).
   // CHECK:STDERR:   return F(T);
   // CHECK:STDERR:          ^~
-  // CHECK:STDERR: fail_different_return_type.carbon:[[@LINE-13]]:1: calling function declared here
+  // CHECK:STDERR: fail_different_return_type.carbon:[[@LINE-13]]:1: note: calling function declared here
   // CHECK:STDERR: fn F(T:! type, U:! type) -> T*;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -51,7 +51,7 @@ fn F(T:! type, U:! type) -> T*;
 // CHECK:STDERR: fail_reorder.carbon:[[@LINE+7]]:6: error: redeclaration differs at parameter 1
 // CHECK:STDERR: fn F(U:! type, T:! type) -> T* {
 // CHECK:STDERR:      ^
-// CHECK:STDERR: fail_reorder.carbon:[[@LINE-5]]:6: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_reorder.carbon:[[@LINE-5]]:6: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: fn F(T:! type, U:! type) -> T*;
 // CHECK:STDERR:      ^
 // CHECK:STDERR:
@@ -59,7 +59,7 @@ fn F(U:! type, T:! type) -> T* {
   // CHECK:STDERR: fail_reorder.carbon:[[@LINE+7]]:10: error: 1 argument(s) passed to function expecting 2 argument(s).
   // CHECK:STDERR:   return F(T);
   // CHECK:STDERR:          ^~
-  // CHECK:STDERR: fail_reorder.carbon:[[@LINE-13]]:1: calling function declared here
+  // CHECK:STDERR: fail_reorder.carbon:[[@LINE-13]]:1: note: calling function declared here
   // CHECK:STDERR: fn F(T:! type, U:! type) -> T*;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -75,7 +75,7 @@ fn F(T:! type, U:! type) -> T*;
 // CHECK:STDERR: fail_rename.carbon:[[@LINE+7]]:6: error: redeclaration differs at parameter 1
 // CHECK:STDERR: fn F(U:! type, T:! type) -> U* {
 // CHECK:STDERR:      ^
-// CHECK:STDERR: fail_rename.carbon:[[@LINE-5]]:6: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_rename.carbon:[[@LINE-5]]:6: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: fn F(T:! type, U:! type) -> T*;
 // CHECK:STDERR:      ^
 // CHECK:STDERR:
@@ -83,7 +83,7 @@ fn F(U:! type, T:! type) -> U* {
   // CHECK:STDERR: fail_rename.carbon:[[@LINE+6]]:10: error: 1 argument(s) passed to function expecting 2 argument(s).
   // CHECK:STDERR:   return F(T);
   // CHECK:STDERR:          ^~
-  // CHECK:STDERR: fail_rename.carbon:[[@LINE-13]]:1: calling function declared here
+  // CHECK:STDERR: fail_rename.carbon:[[@LINE-13]]:1: note: calling function declared here
   // CHECK:STDERR: fn F(T:! type, U:! type) -> T*;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   return F(T);

toolchain/check/testdata/impl/fail_extend_impl_type_as.carbon

@@ -22,7 +22,7 @@ class D {
   // CHECK:STDERR: fail_extend_impl_type_as.carbon:[[@LINE+7]]:3: error: cannot `extend` an `impl` with an explicit self type
   // CHECK:STDERR:   extend impl D as I;
   // CHECK:STDERR:   ^~~~~~
-  // CHECK:STDERR: fail_extend_impl_type_as.carbon:[[@LINE+4]]:15: remove the explicit `Self` type here
+  // CHECK:STDERR: fail_extend_impl_type_as.carbon:[[@LINE+4]]:15: note: remove the explicit `Self` type here
   // CHECK:STDERR:   extend impl D as I;
   // CHECK:STDERR:               ^
   // CHECK:STDERR:
@@ -33,7 +33,7 @@ class E {
   // CHECK:STDERR: fail_extend_impl_type_as.carbon:[[@LINE+6]]:3: error: cannot `extend` an `impl` with an explicit self type
   // CHECK:STDERR:   extend impl Self as I {}
   // CHECK:STDERR:   ^~~~~~
-  // CHECK:STDERR: fail_extend_impl_type_as.carbon:[[@LINE+3]]:15: remove the explicit `Self` type here
+  // CHECK:STDERR: fail_extend_impl_type_as.carbon:[[@LINE+3]]:15: note: remove the explicit `Self` type here
   // CHECK:STDERR:   extend impl Self as I {}
   // CHECK:STDERR:               ^~~~
   extend impl Self as I {}

toolchain/check/testdata/impl/fail_extend_partially_defined_interface.carbon

@@ -13,7 +13,7 @@ interface I {
     // CHECK:STDERR: fail_extend_partially_defined_interface.carbon:[[@LINE+6]]:5: error: `extend impl` requires a definition for interface `I`
     // CHECK:STDERR:     extend impl as I;
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_extend_partially_defined_interface.carbon:[[@LINE-5]]:1: interface is currently being defined
+    // CHECK:STDERR: fail_extend_partially_defined_interface.carbon:[[@LINE-5]]:1: note: interface is currently being defined
     // CHECK:STDERR: interface I {
     // CHECK:STDERR: ^~~~~~~~~~~~~
     extend impl as I;

toolchain/check/testdata/impl/fail_extend_undefined_interface.carbon

@@ -14,7 +14,7 @@ class C {
   // CHECK:STDERR: fail_extend_undefined_interface.carbon:[[@LINE+6]]:3: error: `extend impl` requires a definition for interface `I`
   // CHECK:STDERR:   extend impl as I;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_extend_undefined_interface.carbon:[[@LINE-6]]:1: interface was forward declared here
+  // CHECK:STDERR: fail_extend_undefined_interface.carbon:[[@LINE-6]]:1: note: interface was forward declared here
   // CHECK:STDERR: interface I;
   // CHECK:STDERR: ^~~~~~~~~~~~
   extend impl as I;

toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon

@@ -14,7 +14,7 @@ class NoF {
   // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:3: error: missing implementation of F in impl of interface I
   // CHECK:STDERR:   impl as I {}
   // CHECK:STDERR:   ^~~~~~~~~~~
-  // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-6]]:15: associated function F declared here
+  // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-6]]:15: note: associated function F declared here
   // CHECK:STDERR: interface I { fn F(); }
   // CHECK:STDERR:               ^~~~~~~
   // CHECK:STDERR:
@@ -26,7 +26,7 @@ class FNotFunction {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:5: error: associated function F implemented by non-function
     // CHECK:STDERR:     class F;
     // CHECK:STDERR:     ^~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-18]]:15: associated function F declared here
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-18]]:15: note: associated function F declared here
     // CHECK:STDERR: interface I { fn F(); }
     // CHECK:STDERR:               ^~~~~~~
     // CHECK:STDERR:
@@ -42,7 +42,7 @@ class FAlias {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:11: error: associated function F implemented by non-function
     // CHECK:STDERR:     alias F = PossiblyF;
     // CHECK:STDERR:           ^
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-34]]:15: associated function F declared here
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-34]]:15: note: associated function F declared here
     // CHECK:STDERR: interface I { fn F(); }
     // CHECK:STDERR:               ^~~~~~~
     // CHECK:STDERR:
@@ -55,7 +55,7 @@ class FExtraParam {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:5: error: redeclaration differs because of parameter count of 1
     // CHECK:STDERR:     fn F(b: bool);
     // CHECK:STDERR:     ^~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-47]]:15: previously declared with parameter count of 0
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-47]]:15: note: previously declared with parameter count of 0
     // CHECK:STDERR: interface I { fn F(); }
     // CHECK:STDERR:               ^~~~~~~
     // CHECK:STDERR:
@@ -68,7 +68,7 @@ class FExtraImplicitParam {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:5: error: redeclaration differs because of implicit parameter list
     // CHECK:STDERR:     fn F[self: Self]();
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-60]]:15: previously declared without implicit parameter list
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-60]]:15: note: previously declared without implicit parameter list
     // CHECK:STDERR: interface I { fn F(); }
     // CHECK:STDERR:               ^~~~~~~
     // CHECK:STDERR:
@@ -82,7 +82,7 @@ class FExtraReturnType {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:5: error: function redeclaration differs because return type is `bool`
     // CHECK:STDERR:     fn F() -> bool;
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-74]]:15: previously declared with no return type
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-74]]:15: note: previously declared with no return type
     // CHECK:STDERR: interface I { fn F(); }
     // CHECK:STDERR:               ^~~~~~~
     // CHECK:STDERR:
@@ -97,7 +97,7 @@ class FMissingParam {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:5: error: redeclaration differs because of parameter count of 0
     // CHECK:STDERR:     fn F[self: bool]() -> bool;
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-7]]:15: previously declared with parameter count of 1
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-7]]:15: note: previously declared with parameter count of 1
     // CHECK:STDERR: interface J { fn F[self: bool](b: bool) -> bool; }
     // CHECK:STDERR:               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     // CHECK:STDERR:
@@ -110,7 +110,7 @@ class FMissingImplicitParam {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:5: error: redeclaration differs because of missing implicit parameter list
     // CHECK:STDERR:     fn F(b: bool) -> bool;
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-20]]:15: previously declared with implicit parameter list
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-20]]:15: note: previously declared with implicit parameter list
     // CHECK:STDERR: interface J { fn F[self: bool](b: bool) -> bool; }
     // CHECK:STDERR:               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     // CHECK:STDERR:
@@ -123,7 +123,7 @@ class FMissingReturnType {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:5: error: function redeclaration differs because no return type is provided
     // CHECK:STDERR:     fn F[self: bool](b: bool);
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-33]]:15: previously declared with return type `bool`
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-33]]:15: note: previously declared with return type `bool`
     // CHECK:STDERR: interface J { fn F[self: bool](b: bool) -> bool; }
     // CHECK:STDERR:               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     // CHECK:STDERR:
@@ -136,7 +136,7 @@ class FDifferentParamType {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:22: error: redeclaration differs at parameter 1
     // CHECK:STDERR:     fn F[self: bool](b: Self) -> bool;
     // CHECK:STDERR:                      ^
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-46]]:32: previous declaration's corresponding parameter here
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-46]]:32: note: previous declaration's corresponding parameter here
     // CHECK:STDERR: interface J { fn F[self: bool](b: bool) -> bool; }
     // CHECK:STDERR:                                ^
     // CHECK:STDERR:
@@ -149,7 +149,7 @@ class FDifferentImplicitParamType {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:10: error: redeclaration differs at implicit parameter 1
     // CHECK:STDERR:     fn F[self: Self](b: bool) -> bool;
     // CHECK:STDERR:          ^~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-59]]:20: previous declaration's corresponding implicit parameter here
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-59]]:20: note: previous declaration's corresponding implicit parameter here
     // CHECK:STDERR: interface J { fn F[self: bool](b: bool) -> bool; }
     // CHECK:STDERR:                    ^~~~
     // CHECK:STDERR:
@@ -162,7 +162,7 @@ class FDifferentReturnType {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:5: error: function redeclaration differs because return type is `FDifferentReturnType`
     // CHECK:STDERR:     fn F[self: bool](b: bool) -> Self;
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-72]]:15: previously declared with return type `bool`
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-72]]:15: note: previously declared with return type `bool`
     // CHECK:STDERR: interface J { fn F[self: bool](b: bool) -> bool; }
     // CHECK:STDERR:               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     // CHECK:STDERR:
@@ -176,7 +176,7 @@ class FDifferentParamName {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:22: error: redeclaration differs at parameter 1
     // CHECK:STDERR:     fn F[self: bool](not_b: bool) -> bool;
     // CHECK:STDERR:                      ^~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-86]]:32: previous declaration's corresponding parameter here
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-86]]:32: note: previous declaration's corresponding parameter here
     // CHECK:STDERR: interface J { fn F[self: bool](b: bool) -> bool; }
     // CHECK:STDERR:                                ^
     // CHECK:STDERR:
@@ -193,7 +193,7 @@ class SelfNestedBadParam {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+7]]:10: error: redeclaration differs at parameter 1
     // CHECK:STDERR:     fn F(x: (SelfNestedBadParam*, {.x: i32, .y: i32})) -> [SelfNestedBadParam; 4];
     // CHECK:STDERR:          ^
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-8]]:8: previous declaration's corresponding parameter here
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-8]]:8: note: previous declaration's corresponding parameter here
     // CHECK:STDERR:   fn F(x: (Self*, {.x: Self, .y: i32})) -> [Self; 4];
     // CHECK:STDERR:        ^
     // CHECK:STDERR:
@@ -206,7 +206,7 @@ class SelfNestedBadReturnType {
     // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE+6]]:5: error: function redeclaration differs because return type is `[SelfNestedBadParam; 4]`
     // CHECK:STDERR:     fn F(x: (SelfNestedBadReturnType*, {.x: SelfNestedBadReturnType, .y: i32})) -> [SelfNestedBadParam; 4];
     // CHECK:STDERR:     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-21]]:3: previously declared with return type `[SelfNestedBadReturnType; 4]`
+    // CHECK:STDERR: fail_impl_bad_assoc_fn.carbon:[[@LINE-21]]:3: note: previously declared with return type `[SelfNestedBadReturnType; 4]`
     // CHECK:STDERR:   fn F(x: (Self*, {.x: Self, .y: i32})) -> [Self; 4];
     // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     fn F(x: (SelfNestedBadReturnType*, {.x: SelfNestedBadReturnType, .y: i32})) -> [SelfNestedBadParam; 4];

toolchain/check/testdata/impl/fail_impl_bad_interface.carbon

@@ -15,7 +15,7 @@
 // CHECK:STDERR: fail_impl_bad_interface.carbon:[[@LINE+6]]:13: error: cannot implicitly convert from `bool` to `type`
 // CHECK:STDERR: impl i32 as false {}
 // CHECK:STDERR:             ^~~~~
-// CHECK:STDERR: fail_impl_bad_interface.carbon:[[@LINE+3]]:13: type `bool` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_impl_bad_interface.carbon:[[@LINE+3]]:13: note: type `bool` does not implement interface `ImplicitAs`
 // CHECK:STDERR: impl i32 as false {}
 // CHECK:STDERR:             ^~~~~
 impl i32 as false {}

toolchain/check/testdata/impl/fail_redefinition.carbon

@@ -15,7 +15,7 @@ impl i32 as I {}
 // CHECK:STDERR: fail_redefinition.carbon:[[@LINE+6]]:1: error: redefinition of `impl i32 as I`
 // CHECK:STDERR: impl i32 as I {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redefinition.carbon:[[@LINE-5]]:1: previous definition was here
+// CHECK:STDERR: fail_redefinition.carbon:[[@LINE-5]]:1: note: previous definition was here
 // CHECK:STDERR: impl i32 as I {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~
 impl i32 as I {}

toolchain/check/testdata/index/fail_array_non_int_indexing.carbon

@@ -12,7 +12,7 @@ var a: [i32; 1] = (12,);
 // CHECK:STDERR: fail_array_non_int_indexing.carbon:[[@LINE+6]]:16: error: cannot implicitly convert from `f64` to `i32`
 // CHECK:STDERR: var b: i32 = a[2.6];
 // CHECK:STDERR:                ^~~
-// CHECK:STDERR: fail_array_non_int_indexing.carbon:[[@LINE+3]]:16: type `f64` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_array_non_int_indexing.carbon:[[@LINE+3]]:16: note: type `f64` does not implement interface `ImplicitAs`
 // CHECK:STDERR: var b: i32 = a[2.6];
 // CHECK:STDERR:                ^~~
 var b: i32 = a[2.6];

toolchain/check/testdata/interface/fail_assoc_const_bad_default.carbon

@@ -12,7 +12,7 @@ interface I {
   // CHECK:STDERR: fail_assoc_const_bad_default.carbon:[[@LINE+6]]:3: error: cannot implicitly convert from `i32` to `type`
   // CHECK:STDERR:   let T:! type = 42;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_assoc_const_bad_default.carbon:[[@LINE+3]]:3: type `i32` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_assoc_const_bad_default.carbon:[[@LINE+3]]:3: note: type `i32` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   let T:! type = 42;
   // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~
   let T:! type = 42;

toolchain/check/testdata/interface/fail_todo_define_default_fn_out_of_line.carbon

@@ -27,7 +27,7 @@ interface Interface {
 // CHECK:STDERR: fail_todo_define_default_fn_out_of_line.carbon:[[@LINE+7]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn Interface.F() {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_todo_define_default_fn_out_of_line.carbon:[[@LINE-12]]:3: name is previously declared here
+// CHECK:STDERR: fail_todo_define_default_fn_out_of_line.carbon:[[@LINE-12]]:3: note: name is previously declared here
 // CHECK:STDERR:   default fn F();
 // CHECK:STDERR:   ^~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -36,7 +36,7 @@ fn Interface.F() {}
 // CHECK:STDERR: fail_todo_define_default_fn_out_of_line.carbon:[[@LINE+6]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn Interface.G(a: i32, b: i32) -> i32 = "int.sadd";
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_todo_define_default_fn_out_of_line.carbon:[[@LINE-15]]:3: name is previously declared here
+// CHECK:STDERR: fail_todo_define_default_fn_out_of_line.carbon:[[@LINE-15]]:3: note: name is previously declared here
 // CHECK:STDERR:   default fn G(a: i32, b: i32) -> i32;
 // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 fn Interface.G(a: i32, b: i32) -> i32 = "int.sadd";

toolchain/check/testdata/interface/no_prelude/fail_definition_imported.carbon

@@ -19,13 +19,11 @@ interface I;
 library "[[@TEST_NAME]]";
 import library "a";
 
-// CHECK:STDERR: fail_b.carbon:[[@LINE+9]]:1: error: duplicate name being declared in the same scope
+// CHECK:STDERR: fail_b.carbon:[[@LINE+7]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: interface I {}
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR: fail_b.carbon:[[@LINE-5]]:1: in import
-// CHECK:STDERR: import library "a";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: a.carbon:4:1: name is previously declared here
+// CHECK:STDERR: a.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: interface I;
 // CHECK:STDERR: ^~~~~~~~~~~~
 interface I {}

toolchain/check/testdata/interface/no_prelude/fail_duplicate.carbon

@@ -17,7 +17,7 @@ interface Interface { }
 // CHECK:STDERR: fail_redefine_without_dependents.carbon:[[@LINE+7]]:1: error: redefinition of `interface Interface`
 // CHECK:STDERR: interface Interface {
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redefine_without_dependents.carbon:[[@LINE-5]]:1: previously defined here
+// CHECK:STDERR: fail_redefine_without_dependents.carbon:[[@LINE-5]]:1: note: previously defined here
 // CHECK:STDERR: interface Interface { }
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -34,7 +34,7 @@ interface Interface {}
 // CHECK:STDERR: fail_redefine_with_dependents.carbon:[[@LINE+7]]:1: error: redefinition of `interface Interface`
 // CHECK:STDERR: interface Interface {
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_redefine_with_dependents.carbon:[[@LINE-5]]:1: previously defined here
+// CHECK:STDERR: fail_redefine_with_dependents.carbon:[[@LINE-5]]:1: note: previously defined here
 // CHECK:STDERR: interface Interface {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -51,7 +51,7 @@ fn Function();
 // CHECK:STDERR: fail_name_conflict_with_fn.carbon:[[@LINE+7]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: interface Function;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_name_conflict_with_fn.carbon:[[@LINE-5]]:1: name is previously declared here
+// CHECK:STDERR: fail_name_conflict_with_fn.carbon:[[@LINE-5]]:1: note: name is previously declared here
 // CHECK:STDERR: fn Function();
 // CHECK:STDERR: ^~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -64,7 +64,7 @@ class Class;
 // CHECK:STDERR: fail_name_conflict_with_class.carbon:[[@LINE+6]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: interface Class { }
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_name_conflict_with_class.carbon:[[@LINE-5]]:1: name is previously declared here
+// CHECK:STDERR: fail_name_conflict_with_class.carbon:[[@LINE-5]]:1: note: name is previously declared here
 // CHECK:STDERR: class Class;
 // CHECK:STDERR: ^~~~~~~~~~~~
 interface Class { }

toolchain/check/testdata/interface/no_prelude/fail_generic_redeclaration.carbon

@@ -12,7 +12,7 @@ interface NotGeneric;
 // CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE+7]]:1: error: redeclaration differs because of parameter list
 // CHECK:STDERR: interface NotGeneric(T:! type) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE-4]]:1: previously declared without parameter list
+// CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE-4]]:1: note: previously declared without parameter list
 // CHECK:STDERR: interface NotGeneric;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -22,7 +22,7 @@ interface Generic(T:! type);
 // CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE+7]]:1: error: redeclaration differs because of missing parameter list
 // CHECK:STDERR: interface Generic {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE-4]]:1: previously declared with parameter list
+// CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE-4]]:1: note: previously declared with parameter list
 // CHECK:STDERR: interface Generic(T:! type);
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -32,7 +32,7 @@ interface DifferentParams(T:! type);
 // CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE+6]]:27: error: redeclaration differs at parameter 1
 // CHECK:STDERR: interface DifferentParams(T:! ()) {}
 // CHECK:STDERR:                           ^
-// CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE-4]]:27: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_generic_redeclaration.carbon:[[@LINE-4]]:27: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: interface DifferentParams(T:! type);
 // CHECK:STDERR:                           ^
 interface DifferentParams(T:! ()) {}

toolchain/check/testdata/interface/no_prelude/fail_lookup_undefined.carbon

@@ -13,7 +13,7 @@ interface Undefined;
 // CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE+7]]:4: error: cannot declare a member of undefined interface `Undefined`
 // CHECK:STDERR: fn Undefined.F();
 // CHECK:STDERR:    ^~~~~~~~~
-// CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE-5]]:1: interface was forward declared here
+// CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE-5]]:1: note: interface was forward declared here
 // CHECK:STDERR: interface Undefined;
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -23,7 +23,7 @@ fn Test() {
   // CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE+7]]:3: error: member access into undefined interface `Undefined`
   // CHECK:STDERR:   Undefined.G();
   // CHECK:STDERR:   ^~~~~~~~~~~
-  // CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE-15]]:1: interface was forward declared here
+  // CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE-15]]:1: note: interface was forward declared here
   // CHECK:STDERR: interface Undefined;
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -34,7 +34,7 @@ interface BeingDefined {
   // CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE+11]]:13: error: member access into undefined interface `BeingDefined`
   // CHECK:STDERR:   fn H() -> BeingDefined.T;
   // CHECK:STDERR:             ^~~~~~~~~~~~~~
-  // CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE-4]]:1: interface is currently being defined
+  // CHECK:STDERR: fail_lookup_undefined.carbon:[[@LINE-4]]:1: note: interface is currently being defined
   // CHECK:STDERR: interface BeingDefined {
   // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~
   // CHECK:STDERR:

toolchain/check/testdata/interface/no_prelude/fail_redeclare_member.carbon

@@ -13,7 +13,7 @@ interface Interface {
   // CHECK:STDERR: fail_redeclare_member.carbon:[[@LINE+6]]:3: error: duplicate name being declared in the same scope
   // CHECK:STDERR:   fn F();
   // CHECK:STDERR:   ^~~~~~~
-  // CHECK:STDERR: fail_redeclare_member.carbon:[[@LINE-4]]:3: name is previously declared here
+  // CHECK:STDERR: fail_redeclare_member.carbon:[[@LINE-4]]:3: note: name is previously declared here
   // CHECK:STDERR:   fn F();
   // CHECK:STDERR:   ^~~~~~~
   fn F();

toolchain/check/testdata/interface/no_prelude/fail_todo_generic_default_fn.carbon

@@ -16,7 +16,7 @@ interface I(T:! type) {
 // CHECK:STDERR: fail_todo_generic_default_fn.carbon:[[@LINE+6]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn I(T:! type).F[self: Self]() -> Self { return self; }
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_todo_generic_default_fn.carbon:[[@LINE-6]]:3: name is previously declared here
+// CHECK:STDERR: fail_todo_generic_default_fn.carbon:[[@LINE-6]]:3: note: name is previously declared here
 // CHECK:STDERR:   fn F[self: Self]() -> Self;
 // CHECK:STDERR:   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
 fn I(T:! type).F[self: Self]() -> Self { return self; }

toolchain/check/testdata/interface/no_prelude/generic.carbon

@@ -52,7 +52,7 @@ fn G(T:! Generic(B)) {
   // CHECK:STDERR: fail_mismatched_args.carbon:[[@LINE+6]]:3: error: package `Core` implicitly referenced here, but not found
   // CHECK:STDERR:   F(T);
   // CHECK:STDERR:   ^~
-  // CHECK:STDERR: fail_mismatched_args.carbon:[[@LINE-6]]:6: initializing generic parameter `T` declared here
+  // CHECK:STDERR: fail_mismatched_args.carbon:[[@LINE-6]]:6: note: initializing generic parameter `T` declared here
   // CHECK:STDERR: fn F(T:! Generic(A));
   // CHECK:STDERR:      ^
   F(T);

toolchain/check/testdata/interface/no_prelude/syntactic_merge.carbon

@@ -40,7 +40,7 @@ interface Foo(a:! C);
 // CHECK:STDERR: fail_parens.carbon:[[@LINE+7]]:19: error: redeclaration syntax differs here
 // CHECK:STDERR: interface Foo(a:! (C)) {}
 // CHECK:STDERR:                   ^
-// CHECK:STDERR: fail_parens.carbon:[[@LINE-4]]:19: comparing with previous declaration here
+// CHECK:STDERR: fail_parens.carbon:[[@LINE-4]]:19: note: comparing with previous declaration here
 // CHECK:STDERR: interface Foo(a:! C);
 // CHECK:STDERR:                   ^
 // CHECK:STDERR:
@@ -69,24 +69,20 @@ interface Bar(a:! D);
 
 impl library "[[@TEST_NAME]]";
 
-// CHECK:STDERR: fail_todo_two_file.impl.carbon:[[@LINE+10]]:1: error: duplicate name being declared in the same scope
+// CHECK:STDERR: fail_todo_two_file.impl.carbon:[[@LINE+8]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: interface Foo(a:! C) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_todo_two_file.impl.carbon:[[@LINE-5]]:6: in import
-// CHECK:STDERR: impl library "two_file";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: two_file.carbon:7:1: name is previously declared here
+// CHECK:STDERR: two_file.carbon:7:1: note: name is previously declared here
 // CHECK:STDERR: interface Foo(a:! C);
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
 interface Foo(a:! C) {}
-// CHECK:STDERR: fail_todo_two_file.impl.carbon:[[@LINE+10]]:1: error: duplicate name being declared in the same scope
+// CHECK:STDERR: fail_todo_two_file.impl.carbon:[[@LINE+8]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: interface Bar(a:! D) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~
-// CHECK:STDERR: fail_todo_two_file.impl.carbon:[[@LINE-16]]:6: in import
-// CHECK:STDERR: impl library "two_file";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: two_file.carbon:8:1: name is previously declared here
+// CHECK:STDERR: fail_todo_two_file.impl.carbon:[[@LINE-14]]:6: in import
+// CHECK:STDERR: two_file.carbon:8:1: note: name is previously declared here
 // CHECK:STDERR: interface Bar(a:! D);
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -103,7 +99,7 @@ interface Foo(a:! C);
 // CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE+7]]:15: error: redeclaration differs at parameter 1
 // CHECK:STDERR: interface Foo(b:! D) {}
 // CHECK:STDERR:               ^
-// CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE-4]]:15: previous declaration's corresponding parameter here
+// CHECK:STDERR: fail_name_mismatch.carbon:[[@LINE-4]]:15: note: previous declaration's corresponding parameter here
 // CHECK:STDERR: interface Foo(a:! C);
 // CHECK:STDERR:               ^
 // CHECK:STDERR:
@@ -120,7 +116,7 @@ interface Foo(a:! C);
 // CHECK:STDERR: fail_alias.carbon:[[@LINE+7]]:19: error: redeclaration syntax differs here
 // CHECK:STDERR: interface Foo(a:! D) {}
 // CHECK:STDERR:                   ^
-// CHECK:STDERR: fail_alias.carbon:[[@LINE-4]]:19: comparing with previous declaration here
+// CHECK:STDERR: fail_alias.carbon:[[@LINE-4]]:19: note: comparing with previous declaration here
 // CHECK:STDERR: interface Foo(a:! C);
 // CHECK:STDERR:                   ^
 // CHECK:STDERR:
@@ -137,7 +133,7 @@ interface Foo[a:! C]();
 // CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE+7]]:19: error: redeclaration syntax differs here
 // CHECK:STDERR: interface Foo[a:! D]() {}
 // CHECK:STDERR:                   ^
-// CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE-4]]:19: comparing with previous declaration here
+// CHECK:STDERR: fail_deduced_alias.carbon:[[@LINE-4]]:19: note: comparing with previous declaration here
 // CHECK:STDERR: interface Foo[a:! C]();
 // CHECK:STDERR:                   ^
 // CHECK:STDERR:
@@ -160,13 +156,11 @@ alias D = C;
 // TODO: This fails because importing interfaces doesn't work well. It should
 // fail due to `C` versus `D`, but may succeed if importing interfaces is fixed
 // before syntax matching on imports is supported.
-// CHECK:STDERR: fail_alias_two_file.impl.carbon:[[@LINE+10]]:1: error: duplicate name being declared in the same scope
+// CHECK:STDERR: fail_alias_two_file.impl.carbon:[[@LINE+8]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: interface Foo(a:! D) {}
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR: fail_alias_two_file.impl.carbon:[[@LINE-10]]:6: in import
-// CHECK:STDERR: impl library "alias_two_file";
-// CHECK:STDERR:      ^~~~~~~
-// CHECK:STDERR: alias_two_file.carbon:6:1: name is previously declared here
+// CHECK:STDERR: alias_two_file.carbon:6:1: note: name is previously declared here
 // CHECK:STDERR: interface Foo(a:! C);
 // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -186,7 +180,7 @@ interface Foo(a:! const C);
 // CHECK:STDERR: fail_repeat_const.carbon:[[@LINE+6]]:25: error: redeclaration syntax differs here
 // CHECK:STDERR: interface Foo(a:! const (const C)) {}
 // CHECK:STDERR:                         ^
-// CHECK:STDERR: fail_repeat_const.carbon:[[@LINE-8]]:25: comparing with previous declaration here
+// CHECK:STDERR: fail_repeat_const.carbon:[[@LINE-8]]:25: note: comparing with previous declaration here
 // CHECK:STDERR: interface Foo(a:! const C);
 // CHECK:STDERR:                         ^
 interface Foo(a:! const (const C)) {}
@@ -599,15 +593,15 @@ interface Foo(a:! const (const C)) {}
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %default.import.loc2_6.1 = import <invalid>
 // CHECK:STDOUT:   %default.import.loc2_6.2 = import <invalid>
-// CHECK:STDOUT:   %.decl.loc14: %.type.1 = interface_decl @.1 [template = constants.%.4] {
+// CHECK:STDOUT:   %.decl.loc12: %.type.1 = interface_decl @.1 [template = constants.%.4] {
 // CHECK:STDOUT:     %C.ref: type = name_ref C, imports.%import_ref.1 [template = constants.%C]
-// CHECK:STDOUT:     %a.loc14_15.1: %C = param a, runtime_param<invalid>
-// CHECK:STDOUT:     %a.loc14_15.2: %C = bind_symbolic_name a 0, %a.loc14_15.1 [symbolic = @.1.%a (constants.%a)]
+// CHECK:STDOUT:     %a.loc12_15.1: %C = param a, runtime_param<invalid>
+// CHECK:STDOUT:     %a.loc12_15.2: %C = bind_symbolic_name a 0, %a.loc12_15.1 [symbolic = @.1.%a (constants.%a)]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.decl.loc25: %.type.2 = interface_decl @.2 [template = constants.%.6] {
+// CHECK:STDOUT:   %.decl.loc21: %.type.2 = interface_decl @.2 [template = constants.%.6] {
 // CHECK:STDOUT:     %D.ref: type = name_ref D, imports.%import_ref.2 [template = constants.%C]
-// CHECK:STDOUT:     %a.loc25_15.1: %C = param a, runtime_param<invalid>
-// CHECK:STDOUT:     %a.loc25_15.2: %C = bind_symbolic_name a 0, %a.loc25_15.1 [symbolic = @.2.%a (constants.%a)]
+// CHECK:STDOUT:     %a.loc21_15.1: %C = param a, runtime_param<invalid>
+// CHECK:STDOUT:     %a.loc21_15.2: %C = bind_symbolic_name a 0, %a.loc21_15.1 [symbolic = @.2.%a (constants.%a)]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -617,7 +611,7 @@ interface Foo(a:! const (const C)) {}
 // CHECK:STDOUT:   interface;
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: generic interface @.1(file.%a.loc14_15.2: %C) {
+// CHECK:STDOUT: generic interface @.1(file.%a.loc12_15.2: %C) {
 // CHECK:STDOUT:   %a: %C = bind_symbolic_name a 0 [symbolic = %a (constants.%a)]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !definition:
@@ -639,7 +633,7 @@ interface Foo(a:! const (const C)) {}
 // CHECK:STDOUT:   interface;
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: generic interface @.2(file.%a.loc25_15.2: %C) {
+// CHECK:STDOUT: generic interface @.2(file.%a.loc21_15.2: %C) {
 // CHECK:STDOUT:   %a: %C = bind_symbolic_name a 0 [symbolic = %a (constants.%a)]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !definition:
@@ -995,8 +989,8 @@ interface Foo(a:! const (const C)) {}
 // CHECK:STDOUT:   %D: type = bind_alias D, imports.%import_ref.1 [template = constants.%C]
 // CHECK:STDOUT:   %.decl: %.type = interface_decl @.1 [template = constants.%.4] {
 // CHECK:STDOUT:     %D.ref: type = name_ref D, %D [template = constants.%C]
-// CHECK:STDOUT:     %a.loc19_15.1: %C = param a, runtime_param<invalid>
-// CHECK:STDOUT:     %a.loc19_15.2: %C = bind_symbolic_name a 0, %a.loc19_15.1 [symbolic = @.1.%a (constants.%a)]
+// CHECK:STDOUT:     %a.loc17_15.1: %C = param a, runtime_param<invalid>
+// CHECK:STDOUT:     %a.loc17_15.2: %C = bind_symbolic_name a 0, %a.loc17_15.1 [symbolic = @.1.%a (constants.%a)]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -1006,7 +1000,7 @@ interface Foo(a:! const (const C)) {}
 // CHECK:STDOUT:   interface;
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: generic interface @.1(file.%a.loc19_15.2: %C) {
+// CHECK:STDOUT: generic interface @.1(file.%a.loc17_15.2: %C) {
 // CHECK:STDOUT:   %a: %C = bind_symbolic_name a 0 [symbolic = %a (constants.%a)]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !definition:

toolchain/check/testdata/let/fail_duplicate_decl.carbon

@@ -13,7 +13,7 @@ fn F() {
   // CHECK:STDERR: fail_duplicate_decl.carbon:[[@LINE+6]]:7: error: duplicate name being declared in the same scope
   // CHECK:STDERR:   let a: i32 = 2;
   // CHECK:STDERR:       ^
-  // CHECK:STDERR: fail_duplicate_decl.carbon:[[@LINE-4]]:7: name is previously declared here
+  // CHECK:STDERR: fail_duplicate_decl.carbon:[[@LINE-4]]:7: note: name is previously declared here
   // CHECK:STDERR:   let a: i32 = 1;
   // CHECK:STDERR:       ^
   let a: i32 = 2;

toolchain/check/testdata/let/fail_generic.carbon

@@ -14,7 +14,7 @@ fn F(a: i32) -> i32 {
   // CHECK:STDERR: fail_generic.carbon:[[@LINE+7]]:3: error: cannot implicitly convert from `i32` to `T`
   // CHECK:STDERR:   let x: T = 5;
   // CHECK:STDERR:   ^~~~~~~~~~~~~
-  // CHECK:STDERR: fail_generic.carbon:[[@LINE+4]]:3: type `i32` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_generic.carbon:[[@LINE+4]]:3: note: type `i32` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   let x: T = 5;
   // CHECK:STDERR:   ^~~~~~~~~~~~~
   // CHECK:STDERR:
@@ -22,7 +22,7 @@ fn F(a: i32) -> i32 {
   // CHECK:STDERR: fail_generic.carbon:[[@LINE+6]]:3: error: cannot implicitly convert from `T` to `i32`
   // CHECK:STDERR:   return x;
   // CHECK:STDERR:   ^~~~~~~~~
-  // CHECK:STDERR: fail_generic.carbon:[[@LINE+3]]:3: type `<error>` does not implement interface `ImplicitAs`
+  // CHECK:STDERR: fail_generic.carbon:[[@LINE+3]]:3: note: type `<error>` does not implement interface `ImplicitAs`
   // CHECK:STDERR:   return x;
   // CHECK:STDERR:   ^~~~~~~~~
   return x;

toolchain/check/testdata/let/fail_generic_import.carbon

@@ -22,7 +22,7 @@ impl package Implicit;
 // CHECK:STDERR: fail_implicit.impl.carbon:[[@LINE+6]]:1: error: cannot implicitly convert from `i32` to `T`
 // CHECK:STDERR: let a: T = 0;
 // CHECK:STDERR: ^~~~~~~~~~~~~
-// CHECK:STDERR: fail_implicit.impl.carbon:[[@LINE+3]]:1: type `i32` does not implement interface `ImplicitAs`
+// CHECK:STDERR: fail_implicit.impl.carbon:[[@LINE+3]]:1: note: type `i32` does not implement interface `ImplicitAs`
 // CHECK:STDERR: let a: T = 0;
 // CHECK:STDERR: ^~~~~~~~~~~~~
 let a: T = 0;

toolchain/check/testdata/let/fail_modifiers.carbon

@@ -39,7 +39,7 @@ virtual let e: i32 = 1;
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:9: error: `final` not allowed on declaration with `default`
 // CHECK:STDERR: default final let f: i32 = 1;
 // CHECK:STDERR:         ^~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `default` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `default` previously appeared here
 // CHECK:STDERR: default final let f: i32 = 1;
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -52,7 +52,7 @@ default final let f: i32 = 1;
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:9: error: `default` repeated on declaration
 // CHECK:STDERR: default default let g: i32 = 1;
 // CHECK:STDERR:         ^~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `default` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `default` previously appeared here
 // CHECK:STDERR: default default let g: i32 = 1;
 // CHECK:STDERR: ^~~~~~~
 // CHECK:STDERR:
@@ -65,7 +65,7 @@ default default let g: i32 = 1;
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:11: error: `private` not allowed on declaration with `protected`
 // CHECK:STDERR: protected private let h: i32 = 1;
 // CHECK:STDERR:           ^~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: `protected` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `protected` previously appeared here
 // CHECK:STDERR: protected private let h: i32 = 1;
 // CHECK:STDERR: ^~~~~~~~~
 // CHECK:STDERR:
@@ -78,7 +78,7 @@ protected private let h: i32 = 1;
 // CHECK:STDERR: fail_modifiers.carbon:[[@LINE+6]]:11: error: `protected` repeated on declaration
 // CHECK:STDERR: protected protected let i: i32 = 1;
 // CHECK:STDERR:           ^~~~~~~~~
-// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+3]]:1: `protected` previously appeared here
+// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+3]]:1: note: `protected` previously appeared here
 // CHECK:STDERR: protected protected let i: i32 = 1;
 // CHECK:STDERR: ^~~~~~~~~
 protected protected let i: i32 = 1;

toolchain/check/testdata/namespace/fail_conflict_after_merge.carbon

@@ -24,13 +24,11 @@ import library "namespace";
 // imported declaration.
 namespace NS;
 
-// CHECK:STDERR: fail_conflict.carbon:[[@LINE+10]]:1: error: duplicate name being declared in the same scope
+// CHECK:STDERR: fail_conflict.carbon:[[@LINE+8]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn NS();
 // CHECK:STDERR: ^~~~~~~~
 // CHECK:STDERR: fail_conflict.carbon:[[@LINE-9]]:1: in import
-// CHECK:STDERR: import library "namespace";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: namespace.carbon:4:1: name is previously declared here
+// CHECK:STDERR: namespace.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: namespace NS;
 // CHECK:STDERR: ^~~~~~~~~~~~~
 // CHECK:STDERR:
@@ -40,13 +38,11 @@ fn NS();
 // we don't move it.
 namespace NS;
 
-// CHECK:STDERR: fail_conflict.carbon:[[@LINE+9]]:1: error: duplicate name being declared in the same scope
+// CHECK:STDERR: fail_conflict.carbon:[[@LINE+7]]:1: error: duplicate name being declared in the same scope
 // CHECK:STDERR: fn NS();
 // CHECK:STDERR: ^~~~~~~~
-// CHECK:STDERR: fail_conflict.carbon:[[@LINE-25]]:1: in import
-// CHECK:STDERR: import library "namespace";
-// CHECK:STDERR: ^~~~~~
-// CHECK:STDERR: namespace.carbon:4:1: name is previously declared here
+// CHECK:STDERR: fail_conflict.carbon:[[@LINE-23]]:1: in import
+// CHECK:STDERR: namespace.carbon:4:1: note: name is previously declared here
 // CHECK:STDERR: namespace NS;
 // CHECK:STDERR: ^~~~~~~~~~~~~
 fn NS();
@@ -108,9 +104,9 @@ fn NS();
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %default.import = import <invalid>
 // CHECK:STDOUT:   %NS.loc8: <namespace> = namespace [template] {}
-// CHECK:STDOUT:   %.decl.loc20: %.type.1 = fn_decl @.1 [template = constants.%.2] {}
-// CHECK:STDOUT:   %NS.loc24: <namespace> = namespace [template] {}
-// CHECK:STDOUT:   %.decl.loc35: %.type.2 = fn_decl @.2 [template = constants.%.3] {}
+// CHECK:STDOUT:   %.decl.loc18: %.type.1 = fn_decl @.1 [template = constants.%.2] {}
+// CHECK:STDOUT:   %NS.loc22: <namespace> = namespace [template] {}
+// CHECK:STDOUT:   %.decl.loc31: %.type.2 = fn_decl @.2 [template = constants.%.3] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @.1();