Create LoadedImportRefs for vtable entries with import insts instead of local insts (#5931)

With help from Richard Smith debugging/identifying this.

Hmm - looks like maybe the Self type import ref may have the same
problem? (or at least it seems to have the same quirk in the semir dump,
where the inst id is mentioned in the `import_ref` insts, but is not
defined elsewhere, has no name, and says `[no loc]`. I'll look into that
separately. (hmm, maybe this is just an unloaded ImportRef, actually)

toolchain/check/import_ref.cpp

@@ -2003,18 +2003,20 @@ static auto TryResolveTypedInst(ImportRefResolver& resolver,
     return ResolveResult::Retry();
   }
 
-  for (auto& vtable_entry_id : lazy_virtual_functions) {
+  for (auto [import_vtable_entry_inst_id, local_vtable_entry_inst_id] :
+       llvm::zip(virtual_functions, lazy_virtual_functions)) {
     // Use LoadedImportRef for imported symbolic constant vtable entries so they
     // can carry attached constants necessary for applying specifics to these
     // constants when they are used.
     auto local_attached_constant_id =
-        resolver.local_constant_values().Get(vtable_entry_id);
+        resolver.local_constant_values().GetAttached(
+            local_vtable_entry_inst_id);
     if (local_attached_constant_id.is_symbolic()) {
-      vtable_entry_id = AddLoadedImportRef(
+      local_vtable_entry_inst_id = AddLoadedImportRef(
           resolver,
           GetSingletonType(resolver.local_context(),
                            SemIR::SpecificFunctionType::TypeInstId),
-          vtable_entry_id, local_attached_constant_id);
+          import_vtable_entry_inst_id, local_attached_constant_id);
     }
   }
 

toolchain/check/testdata/class/virtual_modifiers.carbon

@@ -6732,19 +6732,19 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %Base.F.e26: %Base.F.type.f17 = struct_value () [symbolic]
 // CHECK:STDOUT:   %pattern_type.9f7: type = pattern_type %Base.370 [symbolic]
 // CHECK:STDOUT:   %Base.F.specific_fn.892: <specific function> = specific_function %Base.F.e26, @Base.F(%T) [symbolic]
-// CHECK:STDOUT:   %Base.vtable_ptr.f15b84.1: ref %ptr.454 = vtable_ptr @Base.vtable.1, @Base(%T) [symbolic]
+// CHECK:STDOUT:   %Base.vtable_ptr.16a6e1.1: ref %ptr.454 = vtable_ptr @Base.vtable.1, @Base(%T) [symbolic]
 // CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %Base.370 [symbolic]
-// CHECK:STDOUT:   %Base.vtable_ptr.f15b84.2: ref %ptr.454 = vtable_ptr @Base.vtable.2, @Base(%T) [symbolic]
+// CHECK:STDOUT:   %Base.vtable_ptr.16a6e1.2: ref %ptr.454 = vtable_ptr @Base.vtable.2, @Base(%T) [symbolic]
 // CHECK:STDOUT:   %Base.ea5: type = class_type @Base, @Base(%T1) [concrete]
 // CHECK:STDOUT:   %Base.F.type.d82: type = fn_type @Base.F, @Base(%T1) [concrete]
 // CHECK:STDOUT:   %Base.F.d25: %Base.F.type.d82 = struct_value () [concrete]
 // CHECK:STDOUT:   %pattern_type.3bf: type = pattern_type %Base.ea5 [concrete]
 // CHECK:STDOUT:   %Base.F.specific_fn.210: <specific function> = specific_function %Base.F.d25, @Base.F(%T1) [concrete]
-// CHECK:STDOUT:   %Base.vtable_ptr.88e: ref %ptr.454 = vtable_ptr @Base.vtable.1, @Base(%T1) [concrete]
+// CHECK:STDOUT:   %Base.vtable_ptr.e8d: ref %ptr.454 = vtable_ptr @Base.vtable.1, @Base(%T1) [concrete]
 // CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
-// CHECK:STDOUT:   %Base.vtable_ptr.f15b84.3: ref %ptr.454 = vtable_ptr @Base.vtable.3, @Base(%T) [symbolic]
+// CHECK:STDOUT:   %Base.vtable_ptr.16a6e1.3: ref %ptr.454 = vtable_ptr @Base.vtable.3, @Base(%T) [symbolic]
 // CHECK:STDOUT:   %.b74: ref %ptr.454 = class_element_access file.%v.var, element0 [concrete]
-// CHECK:STDOUT:   %Base.val: %Base.ea5 = struct_value (%Base.vtable_ptr.88e) [concrete]
+// CHECK:STDOUT:   %Base.val: %Base.ea5 = struct_value (%Base.vtable_ptr.e8d) [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -6753,15 +6753,15 @@ class T2(G2:! type) {
 // CHECK:STDOUT:     import Core//prelude
 // CHECK:STDOUT:     import Core//prelude/...
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %Main.import_ref.03f: ref %ptr.454 = import_ref Main//generic_lib, loc6_1, loaded [symbolic = @Base.%vtable_ptr (constants.%Base.vtable_ptr.f15b84.3)]
+// CHECK:STDOUT:   %Main.import_ref.03f: ref %ptr.454 = import_ref Main//generic_lib, loc6_1, loaded [symbolic = @Base.%vtable_ptr (constants.%Base.vtable_ptr.16a6e1.3)]
 // CHECK:STDOUT:   %Main.import_ref.5ab3ec.1: type = import_ref Main//generic_lib, loc4_17, loaded [symbolic = @Base.%T (constants.%T)]
 // CHECK:STDOUT:   %Main.import_ref.05e: <witness> = import_ref Main//generic_lib, loc6_1, loaded [concrete = constants.%complete_type]
 // CHECK:STDOUT:   %Main.import_ref.8e0 = import_ref Main//generic_lib, inst27 [no loc], unloaded
 // CHECK:STDOUT:   %Main.import_ref.e54 = import_ref Main//generic_lib, loc5_30, unloaded
 // CHECK:STDOUT:   %Main.import_ref.5ab3ec.2: type = import_ref Main//generic_lib, loc4_17, loaded [symbolic = @Base.%T (constants.%T)]
-// CHECK:STDOUT:   %Main.import_ref.4f4e13.1: <specific function> = import_ref Main//generic_lib, inst47 [no loc], loaded [symbolic = constants.%Base.F.specific_fn.892]
-// CHECK:STDOUT:   %Main.import_ref.4f4e13.2: <specific function> = import_ref Main//generic_lib, inst47 [no loc], loaded [symbolic = constants.%Base.F.specific_fn.892]
-// CHECK:STDOUT:   %Main.import_ref.4f4e13.3: <specific function> = import_ref Main//generic_lib, inst47 [no loc], loaded [symbolic = constants.%Base.F.specific_fn.892]
+// CHECK:STDOUT:   %Main.import_ref.78ad15.1: <specific function> = import_ref Main//generic_lib, loc6_1, loaded [symbolic = constants.%Base.F.specific_fn.892]
+// CHECK:STDOUT:   %Main.import_ref.78ad15.2: <specific function> = import_ref Main//generic_lib, loc6_1, loaded [symbolic = constants.%Base.F.specific_fn.892]
+// CHECK:STDOUT:   %Main.import_ref.78ad15.3: <specific function> = import_ref Main//generic_lib, loc6_1, loaded [symbolic = constants.%Base.F.specific_fn.892]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
@@ -6796,7 +6796,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %Base.F.type: type = fn_type @Base.F, @Base(%T) [symbolic = %Base.F.type (constants.%Base.F.type.f17)]
 // CHECK:STDOUT:   %Base.F: @Base.%Base.F.type (%Base.F.type.f17) = struct_value () [symbolic = %Base.F (constants.%Base.F.e26)]
 // CHECK:STDOUT:   %Base.F.specific_fn: <specific function> = specific_function %Base.F, @Base.F(%T) [symbolic = %Base.F.specific_fn (constants.%Base.F.specific_fn.892)]
-// CHECK:STDOUT:   %vtable_ptr: ref %ptr.454 = vtable_ptr @Base.vtable.1, @Base(%T) [symbolic = %vtable_ptr (constants.%Base.vtable_ptr.f15b84.1)]
+// CHECK:STDOUT:   %vtable_ptr: ref %ptr.454 = vtable_ptr @Base.vtable.1, @Base(%T) [symbolic = %vtable_ptr (constants.%Base.vtable_ptr.16a6e1.1)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   class {
 // CHECK:STDOUT:     complete_type_witness = imports.%Main.import_ref.05e
@@ -6809,15 +6809,15 @@ class T2(G2:! type) {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: vtable @Base.vtable.1 {
-// CHECK:STDOUT:   imports.%Main.import_ref.4f4e13.1
+// CHECK:STDOUT:   imports.%Main.import_ref.78ad15.1
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: vtable @Base.vtable.2 {
-// CHECK:STDOUT:   imports.%Main.import_ref.4f4e13.2
+// CHECK:STDOUT:   imports.%Main.import_ref.78ad15.2
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: vtable @Base.vtable.3 {
-// CHECK:STDOUT:   imports.%Main.import_ref.4f4e13.3
+// CHECK:STDOUT:   imports.%Main.import_ref.78ad15.3
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: generic virtual fn @Base.F(imports.%Main.import_ref.5ab3ec.2: type) [from "generic_lib.carbon"] {
@@ -6835,7 +6835,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %.loc7_20.1: %empty_struct_type = struct_literal ()
 // CHECK:STDOUT:   %.loc7_20.2: ref %ptr.454 = class_element_access file.%v.var, element0 [concrete = constants.%.b74]
-// CHECK:STDOUT:   %.loc7_20.3: init %ptr.454 = initialize_from constants.%Base.vtable_ptr.88e to %.loc7_20.2 [concrete = constants.%Base.vtable_ptr.88e]
+// CHECK:STDOUT:   %.loc7_20.3: init %ptr.454 = initialize_from constants.%Base.vtable_ptr.e8d to %.loc7_20.2 [concrete = constants.%Base.vtable_ptr.e8d]
 // CHECK:STDOUT:   %.loc7_20.4: init %Base.ea5 = class_init (%.loc7_20.3), file.%v.var [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc7_1: init %Base.ea5 = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%Base.val]
 // CHECK:STDOUT:   assign file.%v.var, %.loc7_1
@@ -6849,7 +6849,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %Base.F.type => constants.%Base.F.type.f17
 // CHECK:STDOUT:   %Base.F => constants.%Base.F.e26
 // CHECK:STDOUT:   %Base.F.specific_fn => constants.%Base.F.specific_fn.892
-// CHECK:STDOUT:   %vtable_ptr => constants.%Base.vtable_ptr.f15b84.2
+// CHECK:STDOUT:   %vtable_ptr => constants.%Base.vtable_ptr.16a6e1.2
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @Base.F(constants.%T) {
@@ -6868,7 +6868,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %Base.F.type => constants.%Base.F.type.d82
 // CHECK:STDOUT:   %Base.F => constants.%Base.F.d25
 // CHECK:STDOUT:   %Base.F.specific_fn => constants.%Base.F.specific_fn.210
-// CHECK:STDOUT:   %vtable_ptr => constants.%Base.vtable_ptr.88e
+// CHECK:STDOUT:   %vtable_ptr => constants.%Base.vtable_ptr.e8d
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @Base.F(constants.%T1) {