When merging functions, detect uses of imports prior to a redecl. (#3836)

LookupNameInDecl is only called from DeclNameStack, but I'm adding
mark_imports_used there because it feels more consistent. Not sure if we
want a better API boundary. I admit I'm also suspicious of its call to
LookupInCurrentScope but maybe it's okay due to how imports work.

I was choosing to print multiple diagnostics when a declaration is
previously used _and_ doesn't match because I think the "previously
used" is more important, but the "doesn't match" may give an additional
hint about why it didn't work.

The merge.h utility function is because I think we can follow a similar
model for identifying errors with other declarations: classes,
interfaces, etc.

toolchain/check/context.cpp

@@ -227,7 +227,8 @@ auto Context::AddNameToLookup(SemIR::NameId name_id, SemIR::InstId target_id)
 }
 
 auto Context::LookupNameInDecl(SemIR::LocId loc_id, SemIR::NameId name_id,
-                               SemIR::NameScopeId scope_id) -> SemIR::InstId {
+                               SemIR::NameScopeId scope_id,
+                               bool mark_imports_used) -> SemIR::InstId {
   if (!scope_id.is_valid()) {
     // Look for a name in the current scope only. There are two cases where the
     // name would be in an outer scope:
@@ -263,7 +264,8 @@ auto Context::LookupNameInDecl(SemIR::LocId loc_id, SemIR::NameId name_id,
     //
     //    // Error, no `F` in `B`.
     //    fn B.F() {}
-    return LookupNameInExactScope(loc_id, name_id, name_scopes().Get(scope_id));
+    return LookupNameInExactScope(loc_id, name_id, name_scopes().Get(scope_id),
+                                  mark_imports_used);
   }
 }
 
@@ -298,8 +300,8 @@ auto Context::LookupUnqualifiedName(Parse::NodeId node_id,
 // Handles lookup through the import_ir_scopes for LookupNameInExactScope.
 static auto LookupInImportIRScopes(Context& context, SemIRLoc loc,
                                    SemIR::NameId name_id,
-                                   const SemIR::NameScope& scope)
-    -> SemIR::InstId {
+                                   const SemIR::NameScope& scope,
+                                   bool mark_imports_used) -> SemIR::InstId {
   auto identifier_id = name_id.AsIdentifierId();
   llvm::StringRef identifier;
   if (identifier_id.is_valid()) {
@@ -342,7 +344,8 @@ static auto LookupInImportIRScopes(Context& context, SemIRLoc loc,
     if (result_id.is_valid()) {
       MergeImportRef(context, import_inst_id, result_id);
     } else {
-      LoadImportRef(context, import_inst_id, loc);
+      LoadImportRef(context, import_inst_id,
+                    mark_imports_used ? loc : SemIR::LocId::Invalid);
       result_id = import_inst_id;
     }
   }
@@ -351,14 +354,16 @@ static auto LookupInImportIRScopes(Context& context, SemIRLoc loc,
 }
 
 auto Context::LookupNameInExactScope(SemIRLoc loc, SemIR::NameId name_id,
-                                     const SemIR::NameScope& scope)
-    -> SemIR::InstId {
+                                     const SemIR::NameScope& scope,
+                                     bool mark_imports_used) -> SemIR::InstId {
   if (auto it = scope.names.find(name_id); it != scope.names.end()) {
-    LoadImportRef(*this, it->second, loc);
+    LoadImportRef(*this, it->second,
+                  mark_imports_used ? loc : SemIR::LocId::Invalid);
     return it->second;
   }
   if (!scope.import_ir_scopes.empty()) {
-    return LookupInImportIRScopes(*this, loc, name_id, scope);
+    return LookupInImportIRScopes(*this, loc, name_id, scope,
+                                  mark_imports_used);
   }
   return SemIR::InstId::Invalid;
 }
@@ -375,7 +380,8 @@ auto Context::LookupQualifiedName(Parse::NodeId node_id, SemIR::NameId name_id,
     const auto& scope = name_scopes().Get(scope_ids.pop_back_val());
     has_error |= scope.has_error;
 
-    auto scope_result_id = LookupNameInExactScope(node_id, name_id, scope);
+    auto scope_result_id = LookupNameInExactScope(node_id, name_id, scope,
+                                                  /*mark_imports_used=*/true);
     if (!scope_result_id.is_valid()) {
       // Nothing found in this scope: also look in its extended scopes.
       auto extended = llvm::reverse(scope.extended_scopes);

toolchain/check/context.h

@@ -103,7 +103,8 @@ class Context {
   // declaration, returning the referenced instruction. If scope_id is invalid,
   // uses the current contextual scope.
   auto LookupNameInDecl(SemIR::LocId loc_id, SemIR::NameId name_id,
-                        SemIR::NameScopeId scope_id) -> SemIR::InstId;
+                        SemIR::NameScopeId scope_id, bool mark_imports_used)
+      -> SemIR::InstId;
 
   // Performs an unqualified name lookup, returning the referenced instruction.
   auto LookupUnqualifiedName(Parse::NodeId node_id, SemIR::NameId name_id)
@@ -113,7 +114,8 @@ class Context {
   // instruction. Does not look into extended scopes. Returns an invalid
   // instruction if the name is not found.
   auto LookupNameInExactScope(SemIRLoc loc, SemIR::NameId name_id,
-                              const SemIR::NameScope& scope) -> SemIR::InstId;
+                              const SemIR::NameScope& scope,
+                              bool mark_imports_used) -> SemIR::InstId;
 
   // Performs a qualified name lookup in a specified scope and in scopes that
   // it extends, returning the referenced instruction.

toolchain/check/decl_name_stack.cpp

@@ -168,7 +168,8 @@ auto DeclNameStack::ApplyNameQualifierTo(NameContext& name_context,
   if (TryResolveQualifier(name_context, loc_id)) {
     // For identifier nodes, we need to perform a lookup on the identifier.
     auto resolved_inst_id = context_->LookupNameInDecl(
-        name_context.loc_id, name_id, name_context.target_scope_id);
+        name_context.loc_id, name_id, name_context.target_scope_id,
+        /*mark_imports_used=*/false);
     if (!resolved_inst_id.is_valid()) {
       // Invalid indicates an unresolved name. Store it and return.
       name_context.state = NameContext::State::Unresolved;

toolchain/check/handle_function.cpp

@@ -8,6 +8,7 @@
 #include "toolchain/check/decl_state.h"
 #include "toolchain/check/function.h"
 #include "toolchain/check/interface.h"
+#include "toolchain/check/merge.h"
 #include "toolchain/check/modifiers.h"
 #include "toolchain/parse/tree_node_diagnostic_converter.h"
 #include "toolchain/sem_ir/builtin_function_kind.h"
@@ -168,19 +169,13 @@ static auto BuildFunctionDecl(Context& context,
   auto prev_id =
       context.decl_name_stack().LookupOrAddName(name_context, lookup_result_id);
   if (prev_id.is_valid()) {
-    auto prev_inst = context.insts().Get(prev_id);
-    bool prev_is_import = false;
+    auto prev_inst = ResolvePrevInstForMerge(context, node_id, prev_id);
 
-    if (prev_inst.Is<SemIR::ImportRefUsed>()) {
-      prev_inst =
-          context.insts().Get(context.constant_values().Get(prev_id).inst_id());
-      prev_is_import = true;
-    }
-
-    if (auto existing_function_decl = prev_inst.TryAs<SemIR::FunctionDecl>()) {
+    if (auto existing_function_decl =
+            prev_inst.inst.TryAs<SemIR::FunctionDecl>()) {
       if (MergeFunctionRedecl(context, node_id, function_info, is_definition,
                               existing_function_decl->function_id,
-                              prev_is_import)) {
+                              prev_inst.is_import)) {
         // When merging, use the existing function rather than adding a new one.
         function_decl.function_id = existing_function_decl->function_id;
       }

toolchain/check/impl.cpp

@@ -92,8 +92,8 @@ static auto BuildInterfaceWitness(
     auto decl = context.insts().Get(const_id.inst_id());
     if (auto fn_decl = decl.TryAs<SemIR::FunctionDecl>()) {
       auto& fn = context.functions().Get(fn_decl->function_id);
-      auto impl_decl_id =
-          context.LookupNameInExactScope(decl_id, fn.name_id, impl_scope);
+      auto impl_decl_id = context.LookupNameInExactScope(
+          decl_id, fn.name_id, impl_scope, /*mark_imports_used=*/true);
       if (impl_decl_id.is_valid()) {
         used_decl_ids.push_back(impl_decl_id);
         table.push_back(CheckAssociatedFunctionImplementation(

toolchain/check/merge.cpp

@@ -6,9 +6,34 @@
 
 #include "toolchain/check/function.h"
 #include "toolchain/check/import_ref.h"
+#include "toolchain/sem_ir/typed_insts.h"
 
 namespace Carbon::Check {
 
+auto ResolvePrevInstForMerge(Context& context, Parse::NodeId node_id,
+                             SemIR::InstId prev_inst_id) -> PrevInstForMerge {
+  PrevInstForMerge prev_inst{.inst = context.insts().Get(prev_inst_id),
+                             .is_import = false};
+  if (auto import_ref = prev_inst.inst.TryAs<SemIR::ImportRefUsed>()) {
+    CARBON_DIAGNOSTIC(
+        RedeclOfUsedImport, Error,
+        "Redeclaration of imported entity that was previously used.");
+    CARBON_DIAGNOSTIC(UsedImportLoc, Note, "Import used here.");
+    context.emitter()
+        .Build(node_id, RedeclOfUsedImport)
+        .Note(import_ref->used_id, UsedImportLoc)
+        .Emit();
+
+  } else if (!prev_inst.inst.Is<SemIR::ImportRefLoaded>()) {
+    return prev_inst;
+  }
+
+  prev_inst.is_import = true;
+  prev_inst.inst = context.insts().Get(
+      context.constant_values().Get(prev_inst_id).inst_id());
+  return prev_inst;
+}
+
 // Returns the instruction to consider when merging the given inst_id. Returns
 // nullopt if merging is infeasible and no diagnostic should be printed.
 static auto ResolveMergeableInst(Context& context, SemIR::InstId inst_id)

toolchain/check/merge.h

@@ -10,6 +10,20 @@
 
 namespace Carbon::Check {
 
+struct PrevInstForMerge {
+  // The resolved instruction.
+  SemIR::Inst inst;
+  // Whether an import was encountered during resolution.
+  bool is_import;
+};
+
+// Resolves prev_inst_id for merging (or name conflicts). This handles imports
+// to return the instruction relevant for a merge. If an import is found and was
+// previously used, it notes it, although an invalid redeclaration may diagnose
+// for other reasons too.
+auto ResolvePrevInstForMerge(Context& context, Parse::NodeId node_id,
+                             SemIR::InstId prev_inst_id) -> PrevInstForMerge;
+
 // Merges an import ref at new_inst_id another at prev_inst_id. May print a
 // diagnostic if merging is invalid.
 auto MergeImportRef(Context& context, SemIR::InstId new_inst_id,

toolchain/check/testdata/class/fail_import_misuses.carbon

@@ -82,7 +82,7 @@ var a: Incomplete;
 // CHECK:STDOUT:     .Incomplete = %import_ref.2
 // CHECK:STDOUT:     .a = %a
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %import_ref.1: type = import_ref ir1, inst+1, loc_10 [template = constants.%Empty]
+// CHECK:STDOUT:   %import_ref.1: type = import_ref ir1, inst+1, loaded [template = constants.%Empty]
 // CHECK:STDOUT:   %import_ref.2: type = import_ref ir1, inst+4, loc_15 [template = constants.%Incomplete]
 // CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+2, unloaded
 // CHECK:STDOUT:   %.decl: type = class_decl @.1 [template = constants.%.2] {

toolchain/check/testdata/class/fail_todo_import_forward_decl.carbon

@@ -56,7 +56,7 @@ class ForwardDecl {
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
 // CHECK:STDOUT:     .ForwardDecl = %import_ref
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %import_ref: type = import_ref ir1, inst+1, loc_10 [template = constants.%ForwardDecl]
+// CHECK:STDOUT:   %import_ref: type = import_ref ir1, inst+1, loaded [template = constants.%ForwardDecl]
 // CHECK:STDOUT:   %.decl: type = class_decl @.1 [template = constants.%.1] {
 // CHECK:STDOUT:     %ForwardDecl.decl: invalid = class_decl @ForwardDecl [template = constants.%ForwardDecl] {}
 // CHECK:STDOUT:   }

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

@@ -17,6 +17,9 @@ fn B(b: i32) -> i32;
 fn C(c: (i32,)) -> {.c: i32};
 extern fn D();
 
+namespace NS;
+fn NS.E();
+
 // --- extern_api.carbon
 
 library "extern_api" api;
@@ -26,6 +29,9 @@ extern fn B(b: i32) -> i32;
 extern fn C(c: (i32,)) -> {.c: i32};
 extern fn D();
 
+namespace NS;
+extern fn NS.E();
+
 // ============================================================================
 // Test files
 // ============================================================================
@@ -40,6 +46,7 @@ var a: () = A();
 var b: i32 = B(1);
 var c: {.c: i32} = C((1,));
 var d: () = D();
+var e: () = NS.E();
 
 // --- redecl_api.carbon
 
@@ -51,11 +58,13 @@ extern fn A();
 extern fn B(b: i32) -> i32;
 extern fn C(c: (i32,)) -> {.c: i32};
 extern fn D();
+extern fn NS.E();
 
 var a: () = A();
 var b: i32 = B(1);
 var c: {.c: i32} = C((1,));
 var d: () = D();
+var e: () = NS.E();
 
 // --- redecl_extern_api.carbon
 
@@ -67,11 +76,13 @@ extern fn A();
 extern fn B(b: i32) -> i32;
 extern fn C(c: (i32,)) -> {.c: i32};
 extern fn D();
+extern fn NS.E();
 
 var a: () = A();
 var b: i32 = B(1);
 var c: {.c: i32} = C((1,));
 var d: () = D();
+var e: () = NS.E();
 
 // --- merge.carbon
 
@@ -84,6 +95,7 @@ var a: () = A();
 var b: i32 = B(1);
 var c: {.c: i32} = C((1,));
 var d: () = D();
+var e: () = NS.E();
 
 // --- merge_reverse.carbon
 
@@ -96,6 +108,67 @@ var a: () = A();
 var b: i32 = B(1);
 var c: {.c: i32} = C((1,));
 var d: () = D();
+var e: () = NS.E();
+
+// --- fail_decl_after_use.carbon
+
+library "decl_after_use" api;
+
+import library "extern_api";
+
+var a: () = A();
+
+// CHECK:STDERR: fail_decl_after_use.carbon:[[@LINE+7]]:1: ERROR: Redeclaration of imported entity that was previously used.
+// CHECK:STDERR: fn A();
+// CHECK:STDERR: ^~~~~~~
+// CHECK:STDERR: fail_decl_after_use.carbon:[[@LINE-5]]:13: Import used here.
+// CHECK:STDERR: var a: () = A();
+// CHECK:STDERR:             ^
+// CHECK:STDERR:
+fn A();
+
+// --- fail_decl_after_use_two_errors.carbon
+
+library "decl_after_use_two_errors" api;
+
+import library "extern_api";
+
+var a: () = A();
+
+// CHECK:STDERR: fail_decl_after_use_two_errors.carbon:[[@LINE+17]]:1: ERROR: Redeclaration of imported entity that was previously used.
+// CHECK:STDERR: fn A() -> i32;
+// CHECK:STDERR: ^~~~~~~~~~~~~~
+// CHECK:STDERR: fail_decl_after_use_two_errors.carbon:[[@LINE-5]]:13: Import used here.
+// CHECK:STDERR: var a: () = A();
+// CHECK:STDERR:             ^
+// CHECK:STDERR:
+// CHECK:STDERR: fail_decl_after_use_two_errors.carbon:[[@LINE+10]]:1: ERROR: Function redeclaration differs because return type is `i32`.
+// CHECK:STDERR: fn A() -> i32;
+// CHECK:STDERR: ^~~~~~~~~~~~~~
+// CHECK:STDERR: fail_decl_after_use_two_errors.carbon:[[@LINE-14]]:1: In import.
+// CHECK:STDERR: import library "extern_api";
+// CHECK:STDERR: ^~~~~~
+// CHECK:STDERR: extern_api.carbon:4:1: Previously declared with no return type.
+// CHECK:STDERR: extern fn A();
+// CHECK:STDERR: ^~~~~~~~~~~~~~
+// CHECK:STDERR:
+fn A() -> i32;
+
+// --- fail_extern_after_use.carbon
+
+library "extern_after_use" api;
+
+import library "api";
+
+var a: () = A();
+
+// CHECK:STDERR: fail_extern_after_use.carbon:[[@LINE+6]]:1: ERROR: Redeclaration of imported entity that was previously used.
+// CHECK:STDERR: extern fn A();
+// CHECK:STDERR: ^~~~~~~~~~~~~~
+// CHECK:STDERR: fail_extern_after_use.carbon:[[@LINE-5]]:13: Import used here.
+// CHECK:STDERR: var a: () = A();
+// CHECK:STDERR:             ^
+extern fn A();
 
 // --- unloaded.carbon
 
@@ -130,6 +203,7 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %B
 // CHECK:STDOUT:     .C = %C
 // CHECK:STDOUT:     .D = %D
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %A: <function> = fn_decl @A [template] {}
 // CHECK:STDOUT:   %B: <function> = fn_decl @B [template] {
@@ -146,6 +220,10 @@ import library "extern_api";
 // CHECK:STDOUT:     %return.var.loc6: ref {.c: i32} = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %D: <function> = fn_decl @D [template] {}
+// CHECK:STDOUT:   %NS: <namespace> = namespace [template] {
+// CHECK:STDOUT:     .E = %E
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %E: <function> = fn_decl @E [template] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @A();
@@ -156,6 +234,8 @@ import library "extern_api";
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @D();
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @E();
+// CHECK:STDOUT:
 // CHECK:STDOUT: --- extern_api.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
@@ -170,6 +250,7 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %B
 // CHECK:STDOUT:     .C = %C
 // CHECK:STDOUT:     .D = %D
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %A: <function> = fn_decl @A [template] {}
 // CHECK:STDOUT:   %B: <function> = fn_decl @B [template] {
@@ -186,6 +267,10 @@ import library "extern_api";
 // CHECK:STDOUT:     %return.var.loc6: ref {.c: i32} = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %D: <function> = fn_decl @D [template] {}
+// CHECK:STDOUT:   %NS: <namespace> = namespace [template] {
+// CHECK:STDOUT:     .E = %E
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %E: <function> = fn_decl @E [template] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @A();
@@ -196,6 +281,8 @@ import library "extern_api";
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @D();
 // CHECK:STDOUT:
+// CHECK:STDOUT: extern fn @E();
+// CHECK:STDOUT:
 // CHECK:STDOUT: --- basics.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
@@ -212,15 +299,22 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %import_ref.2
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:     .a = %a
 // CHECK:STDOUT:     .b = %b
 // CHECK:STDOUT:     .c = %c
 // CHECK:STDOUT:     .d = %d
+// CHECK:STDOUT:     .e = %e
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_15 [template = imports.%A]
 // CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+5, loc_24 [template = imports.%B]
 // CHECK:STDOUT:   %import_ref.3: <function> = import_ref ir1, inst+17, loc_39 [template = imports.%C]
 // CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+18, loc_53 [template = imports.%D]
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir1, inst+20, loc_65 [template = imports.%E]
 // CHECK:STDOUT:   %.loc6_9.1: () = tuple_literal ()
 // CHECK:STDOUT:   %.loc6_9.2: type = converted %.loc6_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %a.var: ref () = var a
@@ -234,6 +328,10 @@ import library "extern_api";
 // CHECK:STDOUT:   %.loc9_9.2: type = converted %.loc9_9.1, constants.%.1 [template = constants.%.1]
 // CHECK:STDOUT:   %d.var: ref () = var d
 // CHECK:STDOUT:   %d: ref () = bind_name d, %d.var
+// CHECK:STDOUT:   %.loc10_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc10_9.2: type = converted %.loc10_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %e.var: ref () = var e
+// CHECK:STDOUT:   %e: ref () = bind_name e, %e.var
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @A();
@@ -244,6 +342,8 @@ import library "extern_api";
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @D();
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @E();
+// CHECK:STDOUT:
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %A.ref: <function> = name_ref A, file.%import_ref.1 [template = imports.%A]
@@ -263,6 +363,10 @@ import library "extern_api";
 // CHECK:STDOUT:   %D.ref: <function> = name_ref D, file.%import_ref.4 [template = imports.%D]
 // CHECK:STDOUT:   %.loc9: init () = call %D.ref()
 // CHECK:STDOUT:   assign file.%d.var, %.loc9
+// CHECK:STDOUT:   %NS.ref: <namespace> = name_ref NS, file.%NS [template = file.%NS]
+// CHECK:STDOUT:   %E.ref: <function> = name_ref E, file.%import_ref.6 [template = imports.%E]
+// CHECK:STDOUT:   %.loc10: init () = call %E.ref()
+// CHECK:STDOUT:   assign file.%e.var, %.loc10
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -283,15 +387,22 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %import_ref.2
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:     .a = %a
-// CHECK:STDOUT:     .b = %b.loc12
-// CHECK:STDOUT:     .c = %c.loc13
+// CHECK:STDOUT:     .b = %b.loc13
+// CHECK:STDOUT:     .c = %c.loc14
 // CHECK:STDOUT:     .d = %d
+// CHECK:STDOUT:     .e = %e
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_11 [template = imports.%A]
-// CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+5, loc_17 [template = imports.%B]
-// CHECK:STDOUT:   %import_ref.3: <function> = import_ref ir1, inst+17, loc_28 [template = imports.%C]
-// CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+18, loc_47 [template = imports.%D]
+// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_65 [template = imports.%A]
+// CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+5, loc_74 [template = imports.%B]
+// CHECK:STDOUT:   %import_ref.3: <function> = import_ref ir1, inst+17, loc_89 [template = imports.%C]
+// CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+18, loc_103 [template = imports.%D]
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir1, inst+20, loc_115 [template = imports.%E]
 // CHECK:STDOUT:   %A: <function> = fn_decl @A [template] {}
 // CHECK:STDOUT:   %B: <function> = fn_decl @B [template] {
 // CHECK:STDOUT:     %b.loc7_13.1: i32 = param b
@@ -307,19 +418,24 @@ import library "extern_api";
 // CHECK:STDOUT:     %return.var.loc8: ref {.c: i32} = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %D: <function> = fn_decl @D [template] {}
-// CHECK:STDOUT:   %.loc11_9.1: () = tuple_literal ()
-// CHECK:STDOUT:   %.loc11_9.2: type = converted %.loc11_9.1, constants.%.4 [template = constants.%.4]
+// CHECK:STDOUT:   %E: <function> = fn_decl @E [template] {}
+// CHECK:STDOUT:   %.loc12_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc12_9.2: type = converted %.loc12_9.1, constants.%.4 [template = constants.%.4]
 // CHECK:STDOUT:   %a.var: ref () = var a
 // CHECK:STDOUT:   %a: ref () = bind_name a, %a.var
 // CHECK:STDOUT:   %b.var: ref i32 = var b
-// CHECK:STDOUT:   %b.loc12: ref i32 = bind_name b, %b.var
-// CHECK:STDOUT:   %.loc13: type = struct_type {.c: i32} [template = constants.%.3]
+// CHECK:STDOUT:   %b.loc13: ref i32 = bind_name b, %b.var
+// CHECK:STDOUT:   %.loc14: type = struct_type {.c: i32} [template = constants.%.3]
 // CHECK:STDOUT:   %c.var: ref {.c: i32} = var c
-// CHECK:STDOUT:   %c.loc13: ref {.c: i32} = bind_name c, %c.var
-// CHECK:STDOUT:   %.loc14_9.1: () = tuple_literal ()
-// CHECK:STDOUT:   %.loc14_9.2: type = converted %.loc14_9.1, constants.%.4 [template = constants.%.4]
+// CHECK:STDOUT:   %c.loc14: ref {.c: i32} = bind_name c, %c.var
+// CHECK:STDOUT:   %.loc15_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc15_9.2: type = converted %.loc15_9.1, constants.%.4 [template = constants.%.4]
 // CHECK:STDOUT:   %d.var: ref () = var d
 // CHECK:STDOUT:   %d: ref () = bind_name d, %d.var
+// CHECK:STDOUT:   %.loc16_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc16_9.2: type = converted %.loc16_9.1, constants.%.4 [template = constants.%.4]
+// CHECK:STDOUT:   %e.var: ref () = var e
+// CHECK:STDOUT:   %e: ref () = bind_name e, %e.var
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @A();
@@ -330,25 +446,31 @@ import library "extern_api";
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @D();
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @E();
+// CHECK:STDOUT:
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %A.ref: <function> = name_ref A, file.%import_ref.1 [template = imports.%A]
-// CHECK:STDOUT:   %.loc11: init () = call %A.ref()
-// CHECK:STDOUT:   assign file.%a.var, %.loc11
+// CHECK:STDOUT:   %.loc12: init () = call %A.ref()
+// CHECK:STDOUT:   assign file.%a.var, %.loc12
 // CHECK:STDOUT:   %B.ref: <function> = name_ref B, file.%import_ref.2 [template = imports.%B]
-// CHECK:STDOUT:   %.loc12_16: i32 = int_literal 1 [template = constants.%.5]
-// CHECK:STDOUT:   %.loc12_15: init i32 = call %B.ref(%.loc12_16)
-// CHECK:STDOUT:   assign file.%b.var, %.loc12_15
+// CHECK:STDOUT:   %.loc13_16: i32 = int_literal 1 [template = constants.%.5]
+// CHECK:STDOUT:   %.loc13_15: init i32 = call %B.ref(%.loc13_16)
+// CHECK:STDOUT:   assign file.%b.var, %.loc13_15
 // CHECK:STDOUT:   %C.ref: <function> = name_ref C, file.%import_ref.3 [template = imports.%C]
-// CHECK:STDOUT:   %.loc13_23: i32 = int_literal 1 [template = constants.%.5]
-// CHECK:STDOUT:   %.loc13_25.1: (i32,) = tuple_literal (%.loc13_23)
-// CHECK:STDOUT:   %.loc13_25.2: (i32,) = tuple_value (%.loc13_23) [template = constants.%.6]
-// CHECK:STDOUT:   %.loc13_25.3: (i32,) = converted %.loc13_25.1, %.loc13_25.2 [template = constants.%.6]
-// CHECK:STDOUT:   %.loc13_21: init {.c: i32} = call %C.ref(%.loc13_25.3)
-// CHECK:STDOUT:   assign file.%c.var, %.loc13_21
+// CHECK:STDOUT:   %.loc14_23: i32 = int_literal 1 [template = constants.%.5]
+// CHECK:STDOUT:   %.loc14_25.1: (i32,) = tuple_literal (%.loc14_23)
+// CHECK:STDOUT:   %.loc14_25.2: (i32,) = tuple_value (%.loc14_23) [template = constants.%.6]
+// CHECK:STDOUT:   %.loc14_25.3: (i32,) = converted %.loc14_25.1, %.loc14_25.2 [template = constants.%.6]
+// CHECK:STDOUT:   %.loc14_21: init {.c: i32} = call %C.ref(%.loc14_25.3)
+// CHECK:STDOUT:   assign file.%c.var, %.loc14_21
 // CHECK:STDOUT:   %D.ref: <function> = name_ref D, file.%import_ref.4 [template = imports.%D]
-// CHECK:STDOUT:   %.loc14: init () = call %D.ref()
-// CHECK:STDOUT:   assign file.%d.var, %.loc14
+// CHECK:STDOUT:   %.loc15: init () = call %D.ref()
+// CHECK:STDOUT:   assign file.%d.var, %.loc15
+// CHECK:STDOUT:   %NS.ref: <namespace> = name_ref NS, file.%NS [template = file.%NS]
+// CHECK:STDOUT:   %E.ref: <function> = name_ref E, file.%import_ref.6 [template = imports.%E]
+// CHECK:STDOUT:   %.loc16: init () = call %E.ref()
+// CHECK:STDOUT:   assign file.%e.var, %.loc16
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -369,15 +491,22 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %import_ref.2
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:     .a = %a
-// CHECK:STDOUT:     .b = %b.loc12
-// CHECK:STDOUT:     .c = %c.loc13
+// CHECK:STDOUT:     .b = %b.loc13
+// CHECK:STDOUT:     .c = %c.loc14
 // CHECK:STDOUT:     .d = %d
+// CHECK:STDOUT:     .e = %e
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_11 [template = imports.%A]
-// CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+5, loc_17 [template = imports.%B]
-// CHECK:STDOUT:   %import_ref.3: <function> = import_ref ir1, inst+17, loc_28 [template = imports.%C]
-// CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+18, loc_47 [template = imports.%D]
+// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_65 [template = imports.%A]
+// CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+5, loc_74 [template = imports.%B]
+// CHECK:STDOUT:   %import_ref.3: <function> = import_ref ir1, inst+17, loc_89 [template = imports.%C]
+// CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+18, loc_103 [template = imports.%D]
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir1, inst+20, loc_115 [template = imports.%E]
 // CHECK:STDOUT:   %A: <function> = fn_decl @A [template] {}
 // CHECK:STDOUT:   %B: <function> = fn_decl @B [template] {
 // CHECK:STDOUT:     %b.loc7_13.1: i32 = param b
@@ -393,19 +522,24 @@ import library "extern_api";
 // CHECK:STDOUT:     %return.var.loc8: ref {.c: i32} = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %D: <function> = fn_decl @D [template] {}
-// CHECK:STDOUT:   %.loc11_9.1: () = tuple_literal ()
-// CHECK:STDOUT:   %.loc11_9.2: type = converted %.loc11_9.1, constants.%.4 [template = constants.%.4]
+// CHECK:STDOUT:   %E: <function> = fn_decl @E [template] {}
+// CHECK:STDOUT:   %.loc12_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc12_9.2: type = converted %.loc12_9.1, constants.%.4 [template = constants.%.4]
 // CHECK:STDOUT:   %a.var: ref () = var a
 // CHECK:STDOUT:   %a: ref () = bind_name a, %a.var
 // CHECK:STDOUT:   %b.var: ref i32 = var b
-// CHECK:STDOUT:   %b.loc12: ref i32 = bind_name b, %b.var
-// CHECK:STDOUT:   %.loc13: type = struct_type {.c: i32} [template = constants.%.3]
+// CHECK:STDOUT:   %b.loc13: ref i32 = bind_name b, %b.var
+// CHECK:STDOUT:   %.loc14: type = struct_type {.c: i32} [template = constants.%.3]
 // CHECK:STDOUT:   %c.var: ref {.c: i32} = var c
-// CHECK:STDOUT:   %c.loc13: ref {.c: i32} = bind_name c, %c.var
-// CHECK:STDOUT:   %.loc14_9.1: () = tuple_literal ()
-// CHECK:STDOUT:   %.loc14_9.2: type = converted %.loc14_9.1, constants.%.4 [template = constants.%.4]
+// CHECK:STDOUT:   %c.loc14: ref {.c: i32} = bind_name c, %c.var
+// CHECK:STDOUT:   %.loc15_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc15_9.2: type = converted %.loc15_9.1, constants.%.4 [template = constants.%.4]
 // CHECK:STDOUT:   %d.var: ref () = var d
 // CHECK:STDOUT:   %d: ref () = bind_name d, %d.var
+// CHECK:STDOUT:   %.loc16_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc16_9.2: type = converted %.loc16_9.1, constants.%.4 [template = constants.%.4]
+// CHECK:STDOUT:   %e.var: ref () = var e
+// CHECK:STDOUT:   %e: ref () = bind_name e, %e.var
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @A();
@@ -416,25 +550,31 @@ import library "extern_api";
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @D();
 // CHECK:STDOUT:
+// CHECK:STDOUT: extern fn @E();
+// CHECK:STDOUT:
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %A.ref: <function> = name_ref A, file.%import_ref.1 [template = imports.%A]
-// CHECK:STDOUT:   %.loc11: init () = call %A.ref()
-// CHECK:STDOUT:   assign file.%a.var, %.loc11
+// CHECK:STDOUT:   %.loc12: init () = call %A.ref()
+// CHECK:STDOUT:   assign file.%a.var, %.loc12
 // CHECK:STDOUT:   %B.ref: <function> = name_ref B, file.%import_ref.2 [template = imports.%B]
-// CHECK:STDOUT:   %.loc12_16: i32 = int_literal 1 [template = constants.%.5]
-// CHECK:STDOUT:   %.loc12_15: init i32 = call %B.ref(%.loc12_16)
-// CHECK:STDOUT:   assign file.%b.var, %.loc12_15
+// CHECK:STDOUT:   %.loc13_16: i32 = int_literal 1 [template = constants.%.5]
+// CHECK:STDOUT:   %.loc13_15: init i32 = call %B.ref(%.loc13_16)
+// CHECK:STDOUT:   assign file.%b.var, %.loc13_15
 // CHECK:STDOUT:   %C.ref: <function> = name_ref C, file.%import_ref.3 [template = imports.%C]
-// CHECK:STDOUT:   %.loc13_23: i32 = int_literal 1 [template = constants.%.5]
-// CHECK:STDOUT:   %.loc13_25.1: (i32,) = tuple_literal (%.loc13_23)
-// CHECK:STDOUT:   %.loc13_25.2: (i32,) = tuple_value (%.loc13_23) [template = constants.%.6]
-// CHECK:STDOUT:   %.loc13_25.3: (i32,) = converted %.loc13_25.1, %.loc13_25.2 [template = constants.%.6]
-// CHECK:STDOUT:   %.loc13_21: init {.c: i32} = call %C.ref(%.loc13_25.3)
-// CHECK:STDOUT:   assign file.%c.var, %.loc13_21
+// CHECK:STDOUT:   %.loc14_23: i32 = int_literal 1 [template = constants.%.5]
+// CHECK:STDOUT:   %.loc14_25.1: (i32,) = tuple_literal (%.loc14_23)
+// CHECK:STDOUT:   %.loc14_25.2: (i32,) = tuple_value (%.loc14_23) [template = constants.%.6]
+// CHECK:STDOUT:   %.loc14_25.3: (i32,) = converted %.loc14_25.1, %.loc14_25.2 [template = constants.%.6]
+// CHECK:STDOUT:   %.loc14_21: init {.c: i32} = call %C.ref(%.loc14_25.3)
+// CHECK:STDOUT:   assign file.%c.var, %.loc14_21
 // CHECK:STDOUT:   %D.ref: <function> = name_ref D, file.%import_ref.4 [template = imports.%D]
-// CHECK:STDOUT:   %.loc14: init () = call %D.ref()
-// CHECK:STDOUT:   assign file.%d.var, %.loc14
+// CHECK:STDOUT:   %.loc15: init () = call %D.ref()
+// CHECK:STDOUT:   assign file.%d.var, %.loc15
+// CHECK:STDOUT:   %NS.ref: <namespace> = name_ref NS, file.%NS [template = file.%NS]
+// CHECK:STDOUT:   %E.ref: <function> = name_ref E, file.%import_ref.6 [template = imports.%E]
+// CHECK:STDOUT:   %.loc16: init () = call %E.ref()
+// CHECK:STDOUT:   assign file.%e.var, %.loc16
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -454,19 +594,27 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %import_ref.2
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:     .a = %a
 // CHECK:STDOUT:     .b = %b
 // CHECK:STDOUT:     .c = %c
 // CHECK:STDOUT:     .d = %d
+// CHECK:STDOUT:     .e = %e
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_19 [template = imports.%A.1]
 // CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+5, loc_28 [template = imports.%B.1]
 // CHECK:STDOUT:   %import_ref.3: <function> = import_ref ir1, inst+17, loc_43 [template = imports.%C.1]
 // CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+18, loc_57 [template = imports.%D.1]
-// CHECK:STDOUT:   %import_ref.5: <function> = import_ref ir2, inst+1, loaded [template = imports.%A.2]
-// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir2, inst+5, loaded [template = imports.%B.2]
-// CHECK:STDOUT:   %import_ref.7: <function> = import_ref ir2, inst+17, loaded [template = imports.%C.2]
-// CHECK:STDOUT:   %import_ref.8: <function> = import_ref ir2, inst+18, loaded [template = imports.%D.2]
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir1, inst+20, loc_69 [template = imports.%E.1]
+// CHECK:STDOUT:   %import_ref.7: <function> = import_ref ir2, inst+1, loaded [template = imports.%A.2]
+// CHECK:STDOUT:   %import_ref.8: <function> = import_ref ir2, inst+5, loaded [template = imports.%B.2]
+// CHECK:STDOUT:   %import_ref.9: <function> = import_ref ir2, inst+17, loaded [template = imports.%C.2]
+// CHECK:STDOUT:   %import_ref.10: <function> = import_ref ir2, inst+18, loaded [template = imports.%D.2]
+// CHECK:STDOUT:   %import_ref.11: <function> = import_ref ir2, inst+20, loaded [template = imports.%E.2]
 // CHECK:STDOUT:   %.loc7_9.1: () = tuple_literal ()
 // CHECK:STDOUT:   %.loc7_9.2: type = converted %.loc7_9.1, constants.%.3 [template = constants.%.3]
 // CHECK:STDOUT:   %a.var: ref () = var a
@@ -480,6 +628,10 @@ import library "extern_api";
 // CHECK:STDOUT:   %.loc10_9.2: type = converted %.loc10_9.1, constants.%.3 [template = constants.%.3]
 // CHECK:STDOUT:   %d.var: ref () = var d
 // CHECK:STDOUT:   %d: ref () = bind_name d, %d.var
+// CHECK:STDOUT:   %.loc11_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc11_9.2: type = converted %.loc11_9.1, constants.%.3 [template = constants.%.3]
+// CHECK:STDOUT:   %e.var: ref () = var e
+// CHECK:STDOUT:   %e: ref () = bind_name e, %e.var
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @A.1();
@@ -498,6 +650,10 @@ import library "extern_api";
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @D.2();
 // CHECK:STDOUT:
+// CHECK:STDOUT: extern fn @E.1();
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @E.2();
+// CHECK:STDOUT:
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %A.ref: <function> = name_ref A, file.%import_ref.1 [template = imports.%A.1]
@@ -517,6 +673,10 @@ import library "extern_api";
 // CHECK:STDOUT:   %D.ref: <function> = name_ref D, file.%import_ref.4 [template = imports.%D.1]
 // CHECK:STDOUT:   %.loc10: init () = call %D.ref()
 // CHECK:STDOUT:   assign file.%d.var, %.loc10
+// CHECK:STDOUT:   %NS.ref: <namespace> = name_ref NS, file.%NS [template = file.%NS]
+// CHECK:STDOUT:   %E.ref: <function> = name_ref E, file.%import_ref.6 [template = imports.%E.1]
+// CHECK:STDOUT:   %.loc11: init () = call %E.ref()
+// CHECK:STDOUT:   assign file.%e.var, %.loc11
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -536,19 +696,27 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %import_ref.2
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:     .a = %a
 // CHECK:STDOUT:     .b = %b
 // CHECK:STDOUT:     .c = %c
 // CHECK:STDOUT:     .d = %d
+// CHECK:STDOUT:     .e = %e
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_19 [template = imports.%A.1]
 // CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+5, loc_28 [template = imports.%B.1]
 // CHECK:STDOUT:   %import_ref.3: <function> = import_ref ir1, inst+17, loc_43 [template = imports.%C.1]
 // CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+18, loc_57 [template = imports.%D.1]
-// CHECK:STDOUT:   %import_ref.5: <function> = import_ref ir2, inst+1, loaded [template = imports.%A.2]
-// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir2, inst+5, loaded [template = imports.%B.2]
-// CHECK:STDOUT:   %import_ref.7: <function> = import_ref ir2, inst+17, loaded [template = imports.%C.2]
-// CHECK:STDOUT:   %import_ref.8: <function> = import_ref ir2, inst+18, loaded [template = imports.%D.2]
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir1, inst+20, loc_69 [template = imports.%E.1]
+// CHECK:STDOUT:   %import_ref.7: <function> = import_ref ir2, inst+1, loaded [template = imports.%A.2]
+// CHECK:STDOUT:   %import_ref.8: <function> = import_ref ir2, inst+5, loaded [template = imports.%B.2]
+// CHECK:STDOUT:   %import_ref.9: <function> = import_ref ir2, inst+17, loaded [template = imports.%C.2]
+// CHECK:STDOUT:   %import_ref.10: <function> = import_ref ir2, inst+18, loaded [template = imports.%D.2]
+// CHECK:STDOUT:   %import_ref.11: <function> = import_ref ir2, inst+20, loaded [template = imports.%E.2]
 // CHECK:STDOUT:   %.loc7_9.1: () = tuple_literal ()
 // CHECK:STDOUT:   %.loc7_9.2: type = converted %.loc7_9.1, constants.%.3 [template = constants.%.3]
 // CHECK:STDOUT:   %a.var: ref () = var a
@@ -562,6 +730,10 @@ import library "extern_api";
 // CHECK:STDOUT:   %.loc10_9.2: type = converted %.loc10_9.1, constants.%.3 [template = constants.%.3]
 // CHECK:STDOUT:   %d.var: ref () = var d
 // CHECK:STDOUT:   %d: ref () = bind_name d, %d.var
+// CHECK:STDOUT:   %.loc11_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc11_9.2: type = converted %.loc11_9.1, constants.%.3 [template = constants.%.3]
+// CHECK:STDOUT:   %e.var: ref () = var e
+// CHECK:STDOUT:   %e: ref () = bind_name e, %e.var
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @A.1();
@@ -580,6 +752,10 @@ import library "extern_api";
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @D.2();
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @E.1();
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @E.2();
+// CHECK:STDOUT:
 // CHECK:STDOUT: fn @__global_init() {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %A.ref: <function> = name_ref A, file.%import_ref.1 [template = imports.%A.1]
@@ -599,6 +775,137 @@ import library "extern_api";
 // CHECK:STDOUT:   %D.ref: <function> = name_ref D, file.%import_ref.4 [template = imports.%D.1]
 // CHECK:STDOUT:   %.loc10: init () = call %D.ref()
 // CHECK:STDOUT:   assign file.%d.var, %.loc10
+// CHECK:STDOUT:   %NS.ref: <namespace> = name_ref NS, file.%NS [template = file.%NS]
+// CHECK:STDOUT:   %E.ref: <function> = name_ref E, file.%import_ref.6 [template = imports.%E.1]
+// CHECK:STDOUT:   %.loc11: init () = call %E.ref()
+// CHECK:STDOUT:   assign file.%e.var, %.loc11
+// CHECK:STDOUT:   return
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: --- fail_decl_after_use.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %.1: type = tuple_type () [template]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [template] {
+// CHECK:STDOUT:     .A = %import_ref.1
+// CHECK:STDOUT:     .B = %import_ref.2
+// CHECK:STDOUT:     .C = %import_ref.3
+// CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
+// CHECK:STDOUT:     .a = %a
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_15 [template = imports.%A]
+// CHECK:STDOUT:   %import_ref.2 = import_ref ir1, inst+5, unloaded
+// CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+17, unloaded
+// CHECK:STDOUT:   %import_ref.4 = import_ref ir1, inst+18, unloaded
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6 = import_ref ir1, inst+20, unloaded
+// CHECK:STDOUT:   %.loc6_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc6_9.2: type = converted %.loc6_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %a.var: ref () = var a
+// CHECK:STDOUT:   %a: ref () = bind_name a, %a.var
+// CHECK:STDOUT:   %A: <function> = fn_decl @A [template] {}
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @A();
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @__global_init() {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   %A.ref: <function> = name_ref A, file.%import_ref.1 [template = imports.%A]
+// CHECK:STDOUT:   %.loc6: init () = call %A.ref()
+// CHECK:STDOUT:   assign file.%a.var, %.loc6
+// CHECK:STDOUT:   return
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: --- fail_decl_after_use_two_errors.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %.1: type = tuple_type () [template]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [template] {
+// CHECK:STDOUT:     .A = %import_ref.1
+// CHECK:STDOUT:     .B = %import_ref.2
+// CHECK:STDOUT:     .C = %import_ref.3
+// CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
+// CHECK:STDOUT:     .a = %a
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_15 [template = imports.%A]
+// CHECK:STDOUT:   %import_ref.2 = import_ref ir1, inst+5, unloaded
+// CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+17, unloaded
+// CHECK:STDOUT:   %import_ref.4 = import_ref ir1, inst+18, unloaded
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6 = import_ref ir1, inst+20, unloaded
+// CHECK:STDOUT:   %.loc6_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc6_9.2: type = converted %.loc6_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %a.var: ref () = var a
+// CHECK:STDOUT:   %a: ref () = bind_name a, %a.var
+// CHECK:STDOUT:   %.loc25: <function> = fn_decl @.1 [template] {
+// CHECK:STDOUT:     %return.var: ref i32 = var <return slot>
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: extern fn @A();
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @.1() -> i32;
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @__global_init() {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   %A.ref: <function> = name_ref A, file.%import_ref.1 [template = imports.%A]
+// CHECK:STDOUT:   %.loc6: init () = call %A.ref()
+// CHECK:STDOUT:   assign file.%a.var, %.loc6
+// CHECK:STDOUT:   return
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: --- fail_extern_after_use.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %.1: type = tuple_type () [template]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [template] {
+// CHECK:STDOUT:     .A = %import_ref.1
+// CHECK:STDOUT:     .B = %import_ref.2
+// CHECK:STDOUT:     .C = %import_ref.3
+// CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
+// CHECK:STDOUT:     .a = %a
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_15 [template = imports.%A]
+// CHECK:STDOUT:   %import_ref.2 = import_ref ir1, inst+5, unloaded
+// CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+17, unloaded
+// CHECK:STDOUT:   %import_ref.4 = import_ref ir1, inst+18, unloaded
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6 = import_ref ir1, inst+20, unloaded
+// CHECK:STDOUT:   %.loc6_9.1: () = tuple_literal ()
+// CHECK:STDOUT:   %.loc6_9.2: type = converted %.loc6_9.1, constants.%.1 [template = constants.%.1]
+// CHECK:STDOUT:   %a.var: ref () = var a
+// CHECK:STDOUT:   %a: ref () = bind_name a, %a.var
+// CHECK:STDOUT:   %A: <function> = fn_decl @A [template] {}
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @A();
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @__global_init() {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   %A.ref: <function> = name_ref A, file.%import_ref.1 [template = imports.%A]
+// CHECK:STDOUT:   %.loc6: init () = call %A.ref()
+// CHECK:STDOUT:   assign file.%a.var, %.loc6
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -610,11 +917,17 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %import_ref.2
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %import_ref.1 = import_ref ir1, inst+1, unloaded
 // CHECK:STDOUT:   %import_ref.2 = import_ref ir1, inst+5, unloaded
 // CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+17, unloaded
 // CHECK:STDOUT:   %import_ref.4 = import_ref ir1, inst+18, unloaded
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6 = import_ref ir1, inst+20, unloaded
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- unloaded_extern.carbon
@@ -625,11 +938,17 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %import_ref.2
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %import_ref.1 = import_ref ir1, inst+1, unloaded
 // CHECK:STDOUT:   %import_ref.2 = import_ref ir1, inst+5, unloaded
 // CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+17, unloaded
 // CHECK:STDOUT:   %import_ref.4 = import_ref ir1, inst+18, unloaded
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6 = import_ref ir1, inst+20, unloaded
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- loaded_merge.carbon
@@ -645,15 +964,22 @@ import library "extern_api";
 // CHECK:STDOUT:     .B = %import_ref.2
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
+// CHECK:STDOUT:     .NS = %NS
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loaded [template = imports.%A.1]
 // CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+5, loaded [template = imports.%B.1]
 // CHECK:STDOUT:   %import_ref.3: <function> = import_ref ir1, inst+17, loaded [template = imports.%C.1]
 // CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+18, loaded [template = imports.%D.1]
-// CHECK:STDOUT:   %import_ref.5: <function> = import_ref ir2, inst+1, loaded [template = imports.%A.2]
-// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir2, inst+5, loaded [template = imports.%B.2]
-// CHECK:STDOUT:   %import_ref.7: <function> = import_ref ir2, inst+17, loaded [template = imports.%C.2]
-// CHECK:STDOUT:   %import_ref.8: <function> = import_ref ir2, inst+18, loaded [template = imports.%D.2]
+// CHECK:STDOUT:   %import_ref.5: <namespace> = import_ref ir1, inst+19, loaded
+// CHECK:STDOUT:   %NS: <namespace> = namespace %import_ref.5, [template] {
+// CHECK:STDOUT:     .E = %import_ref.6
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %import_ref.6: <function> = import_ref ir1, inst+20, loaded [template = imports.%E.1]
+// CHECK:STDOUT:   %import_ref.7: <function> = import_ref ir2, inst+1, loaded [template = imports.%A.2]
+// CHECK:STDOUT:   %import_ref.8: <function> = import_ref ir2, inst+5, loaded [template = imports.%B.2]
+// CHECK:STDOUT:   %import_ref.9: <function> = import_ref ir2, inst+17, loaded [template = imports.%C.2]
+// CHECK:STDOUT:   %import_ref.10: <function> = import_ref ir2, inst+18, loaded [template = imports.%D.2]
+// CHECK:STDOUT:   %import_ref.11: <function> = import_ref ir2, inst+20, loaded [template = imports.%E.2]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @A.1();
@@ -672,3 +998,7 @@ import library "extern_api";
 // CHECK:STDOUT:
 // CHECK:STDOUT: extern fn @D.2();
 // CHECK:STDOUT:
+// CHECK:STDOUT: extern fn @E.1();
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @E.2();
+// CHECK:STDOUT:

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

@@ -204,8 +204,8 @@ fn D() {}
 // CHECK:STDOUT:     .C = %import_ref.3
 // CHECK:STDOUT:     .D = %import_ref.4
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loc_10 [template = imports.%A]
-// CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+6, loc_17 [template = imports.%B]
+// CHECK:STDOUT:   %import_ref.1: <function> = import_ref ir1, inst+1, loaded [template = imports.%A]
+// CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir1, inst+6, loaded [template = imports.%B]
 // CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+20, unloaded
 // CHECK:STDOUT:   %import_ref.4 = import_ref ir1, inst+30, unloaded
 // CHECK:STDOUT:   %A: <function> = fn_decl @A [template] {}
@@ -235,7 +235,7 @@ fn D() {}
 // CHECK:STDOUT:   %import_ref.1 = import_ref ir1, inst+1, unloaded
 // CHECK:STDOUT:   %import_ref.2 = import_ref ir1, inst+6, unloaded
 // CHECK:STDOUT:   %import_ref.3 = import_ref ir1, inst+20, unloaded
-// CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+30, loc_11 [template = imports.%D]
+// CHECK:STDOUT:   %import_ref.4: <function> = import_ref ir1, inst+30, loaded [template = imports.%D]
 // CHECK:STDOUT:   %D.loc6: <function> = fn_decl @D [template] {}
 // CHECK:STDOUT:   %D.loc16: <function> = fn_decl @D [template] {}
 // CHECK:STDOUT: }

toolchain/check/testdata/namespace/fail_conflict_imported_namespace_second.carbon

@@ -53,7 +53,7 @@ fn NS.Foo();
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
 // CHECK:STDOUT:     .NS = %import_ref
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %import_ref: <function> = import_ref ir1, inst+1, loc_10 [template = imports.%NS]
+// CHECK:STDOUT:   %import_ref: <function> = import_ref ir1, inst+1, loaded [template = imports.%NS]
 // CHECK:STDOUT:   %.loc16: <namespace> = namespace [template] {}
 // CHECK:STDOUT:   %.loc24: <function> = fn_decl @.1 [template] {}
 // CHECK:STDOUT: }

toolchain/check/testdata/packages/cross_package_import.carbon

@@ -332,7 +332,7 @@ fn Other.G() {}
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %import_ref.1: <namespace> = import_ref ir1, inst+1, loaded
 // CHECK:STDOUT:   %Other: <namespace> = namespace %import_ref.1, [template] {}
-// CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir2, inst+1, loc_16 [template = imports.%F]
+// CHECK:STDOUT:   %import_ref.2: <function> = import_ref ir2, inst+1, loaded [template = imports.%F]
 // CHECK:STDOUT:   %F: <function> = fn_decl @F [template] {}
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/diagnostics/diagnostic_kind.def

@@ -148,6 +148,8 @@ CARBON_DIAGNOSTIC_KIND(ImportSelf)
 CARBON_DIAGNOSTIC_KIND(ExplicitImportApi)
 CARBON_DIAGNOSTIC_KIND(RepeatedImport)
 CARBON_DIAGNOSTIC_KIND(FirstImported)
+CARBON_DIAGNOSTIC_KIND(RedeclOfUsedImport)
+CARBON_DIAGNOSTIC_KIND(UsedImportLoc)
 
 // Function call checking.
 CARBON_DIAGNOSTIC_KIND(AddrSelfIsNonRef)