Make ImplDecls evaluate to themselves. (carbon-language#4352)

Change ImplDecls so they evaluate to themselves in general, rather than
having a special case in import handling that pretends that they do.

toolchain/check/eval.cpp

@@ -1278,6 +1278,7 @@ static auto TryEvalInstInContext(EvalContext& eval_context,
                            .specific_id = SemIR::SpecificId::Invalid},
           Phase::Template);
     }
+
     case CARBON_KIND(SemIR::InterfaceDecl interface_decl): {
       // If the interface has generic parameters, we don't produce an interface
       // type, but a callable whose return value is an interface type.
@@ -1311,10 +1312,12 @@ static auto TryEvalInstInContext(EvalContext& eval_context,
     // These cases are treated as being the unique canonical definition of the
     // corresponding constant value.
     // TODO: This doesn't properly handle redeclarations. Consider adding a
-    // corresponding `Value` inst for each of these cases.
+    // corresponding `Value` inst for each of these cases, or returning the
+    // first declaration.
     case SemIR::AssociatedConstantDecl::Kind:
     case SemIR::BaseDecl::Kind:
     case SemIR::FieldDecl::Kind:
+    case SemIR::ImplDecl::Kind:
     case SemIR::Namespace::Kind:
       return SemIR::ConstantId::ForTemplateConstant(inst_id);
 
@@ -1451,7 +1454,6 @@ static auto TryEvalInstInContext(EvalContext& eval_context,
     case SemIR::Branch::Kind:
     case SemIR::BranchIf::Kind:
     case SemIR::BranchWithArg::Kind:
-    case SemIR::ImplDecl::Kind:
     case SemIR::ImportDecl::Kind:
     case SemIR::Param::Kind:
     case SemIR::RequirementEquivalent::Kind:

toolchain/check/import_ref.cpp

@@ -1580,24 +1580,6 @@ class ImportRefResolver {
         context_.types().GetConstantId(interface_val.type_id()));
   }
 
-  // Forms a constant ID that represents the given instruction ID that denotes
-  // an impl declaration. Impl declarations don't have a constant value, but for
-  // the purposes of importing we pretend that they do.
-  //
-  // TODO: Consider alternative options here. We could make impl declarations
-  // actually evaluate to themselves to avoid this hack.
-  static auto ImplDeclIdAsConstantId(SemIR::InstId impl_decl_id)
-      -> SemIR::ConstantId {
-    return SemIR::ConstantId::ForTemplateConstant(impl_decl_id);
-  }
-
-  // Gets the instruction ID for an impl declaration represented by the
-  // specified constant ID.
-  auto ConstantIdAsImplDeclId(SemIR::ConstantId impl_const_id)
-      -> SemIR::InstId {
-    return context_.constant_values().GetInstId(impl_const_id);
-  }
-
   // Make a declaration of an impl. This is done as a separate step from
   // importing the impl definition in order to resolve cycles.
   auto MakeImplDeclaration(const SemIR::Impl& import_impl)
@@ -1615,7 +1597,7 @@ class ImportRefResolver {
 
     // Write the impl ID into the ImplDecl.
     context_.ReplaceInstBeforeConstantUse(impl_decl_id, impl_decl);
-    return {impl_decl.impl_id, ImplDeclIdAsConstantId(impl_decl_id)};
+    return {impl_decl.impl_id, context_.constant_values().Get(impl_decl_id)};
   }
 
   // Imports the definition of an impl.

toolchain/check/testdata/as/overloaded.carbon

@@ -94,7 +94,7 @@ let n: i32 = ((4 as i32) as X) as i32;
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %X.decl: type = class_decl @X [template = constants.%X] {} {}
-// CHECK:STDOUT:   impl_decl @impl.1 {} {
+// CHECK:STDOUT:   impl_decl @impl.1 [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc15_6.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc15_6.2: type = converted %int.make_type_32, %.loc15_6.1 [template = i32]
@@ -103,7 +103,7 @@ let n: i32 = ((4 as i32) as X) as i32;
 // CHECK:STDOUT:     %X.ref: type = name_ref X, file.%X.decl [template = constants.%X]
 // CHECK:STDOUT:     %.loc15_20: type = interface_type @As, @As(constants.%X) [template = constants.%.8]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   impl_decl @impl.2 {} {
+// CHECK:STDOUT:   impl_decl @impl.2 [template] {} {
 // CHECK:STDOUT:     %X.ref: type = name_ref X, file.%X.decl [template = constants.%X]
 // CHECK:STDOUT:     %Core.ref: <namespace> = name_ref Core, imports.%Core [template = imports.%Core]
 // CHECK:STDOUT:     %As.ref: %As.type = name_ref As, imports.%import_ref.2 [template = constants.%As]

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

@@ -64,7 +64,7 @@ var arr: [i32; 1.(I.F)(2)];
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %I.decl: type = interface_decl @I [template = constants.%.1] {} {}
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc15_6.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc15_6.2: type = converted %int.make_type_32, %.loc15_6.1 [template = i32]

toolchain/check/testdata/function/builtin/no_prelude/call_from_operator.carbon

@@ -145,7 +145,7 @@ var arr: [i32; 1 + 2] = (3, 4, 3 + 4);
 // CHECK:STDOUT:     .arr = %arr
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc6_6.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc6_6.2: type = converted %int.make_type_32, %.loc6_6.1 [template = i32]

toolchain/check/testdata/impl/compound.carbon

@@ -92,7 +92,7 @@ fn InstanceCallIndirect(p: i32*) {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %Simple.decl: type = interface_decl @Simple [template = constants.%.1] {} {}
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc16_6.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc16_6.2: type = converted %int.make_type_32, %.loc16_6.1 [template = i32]

toolchain/check/testdata/impl/declaration.carbon

@@ -44,7 +44,7 @@ impl i32 as I;
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %I.decl: type = interface_decl @I [template = constants.%.1] {} {}
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc13_6.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc13_6.2: type = converted %int.make_type_32, %.loc13_6.1 [template = i32]

toolchain/check/testdata/impl/empty.carbon

@@ -47,7 +47,7 @@ impl i32 as Empty {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %Empty.decl: type = interface_decl @Empty [template = constants.%.1] {} {}
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc14_6.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc14_6.2: type = converted %int.make_type_32, %.loc14_6.1 [template = i32]

toolchain/check/testdata/impl/extend_impl.carbon

@@ -97,7 +97,7 @@ fn G(c: C) {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @C {
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %HasF.ref: type = name_ref HasF, file.%HasF.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc19: <witness> = complete_type_witness %.6 [template = constants.%.7]

toolchain/check/testdata/impl/fail_call_invalid.carbon

@@ -64,7 +64,7 @@ fn InstanceCall(n: i32) {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %Simple.decl: type = interface_decl @Simple [template = constants.%.1] {} {}
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc15_6.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc15_6.2: type = converted %int.make_type_32, %.loc15_6.1 [template = i32]

toolchain/check/testdata/impl/fail_extend_impl_forall.carbon

@@ -121,7 +121,7 @@ class C {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @C {
-// CHECK:STDOUT:   impl_decl @impl {
+// CHECK:STDOUT:   impl_decl @impl [template] {
 // CHECK:STDOUT:     %T.patt: type = symbolic_binding_pattern T 0
 // CHECK:STDOUT:   } {
 // CHECK:STDOUT:     %T.param: type = param T, runtime_param<invalid>

toolchain/check/testdata/impl/fail_extend_impl_scope.carbon

@@ -48,7 +48,7 @@ extend impl i32 as I {}
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %I.decl: type = interface_decl @I [template = constants.%.1] {} {}
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc16_13.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc16_13.2: type = converted %int.make_type_32, %.loc16_13.1 [template = i32]

toolchain/check/testdata/impl/fail_extend_impl_type_as.carbon

@@ -110,7 +110,7 @@ class E {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @C {
-// CHECK:STDOUT:   impl_decl @impl.1 {} {
+// CHECK:STDOUT:   impl_decl @impl.1 [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc18_15.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc18_15.2: type = converted %int.make_type_32, %.loc18_15.1 [template = i32]
@@ -124,7 +124,7 @@ class E {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @D {
-// CHECK:STDOUT:   impl_decl @impl.2 {} {
+// CHECK:STDOUT:   impl_decl @impl.2 [template] {} {
 // CHECK:STDOUT:     %D.ref: type = name_ref D, file.%D.decl [template = constants.%D]
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
@@ -136,7 +136,7 @@ class E {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @E {
-// CHECK:STDOUT:   impl_decl @impl.3 {} {
+// CHECK:STDOUT:   impl_decl @impl.3 [template] {} {
 // CHECK:STDOUT:     %Self.ref: type = name_ref Self, constants.%E [template = constants.%E]
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }

toolchain/check/testdata/impl/fail_extend_non_interface.carbon

@@ -55,7 +55,7 @@ class C {
 // CHECK:STDOUT: class @C {
 // CHECK:STDOUT:   %.loc15_18.1: type = value_of_initializer @impl.%int.make_type_32 [template = i32]
 // CHECK:STDOUT:   %.loc15_18.2: type = converted @impl.%int.make_type_32, %.loc15_18.1 [template = i32]
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc16: <witness> = complete_type_witness %.2 [template = constants.%.3]

toolchain/check/testdata/impl/fail_extend_partially_defined_interface.carbon

@@ -72,7 +72,7 @@ interface I {
 // CHECK:STDOUT: !definition:
 // CHECK:STDOUT:
 // CHECK:STDOUT:   class {
-// CHECK:STDOUT:     impl_decl @impl {} {
+// CHECK:STDOUT:     impl_decl @impl [template] {} {
 // CHECK:STDOUT:       %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:     }
 // CHECK:STDOUT:     %.loc20: <witness> = complete_type_witness %.2 [template = constants.%.3]

toolchain/check/testdata/impl/fail_extend_undefined_interface.carbon

@@ -58,7 +58,7 @@ class C {
 // CHECK:STDOUT: impl @impl: %C as %.1;
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @C {
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc21: <witness> = complete_type_witness %.2 [template = constants.%.3]

toolchain/check/testdata/impl/fail_impl_as_scope.carbon

@@ -54,7 +54,7 @@ impl as Simple {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %Simple.decl: type = interface_decl @Simple [template = constants.%.1] {} {}
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %Simple.ref: type = name_ref Simple, file.%Simple.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }

toolchain/check/testdata/impl/fail_impl_bad_assoc_const.carbon

@@ -49,7 +49,7 @@ impl bool as I {}
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
 // CHECK:STDOUT:   %I.decl: type = interface_decl @I [template = constants.%.1] {} {}
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %bool.make_type: init type = call constants.%Bool() [template = bool]
 // CHECK:STDOUT:     %.loc16_6.1: type = value_of_initializer %bool.make_type [template = bool]
 // CHECK:STDOUT:     %.loc16_6.2: type = converted %bool.make_type, %.loc16_6.1 [template = bool]

toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon

@@ -734,7 +734,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @NoF {
-// CHECK:STDOUT:   impl_decl @impl.1 {} {
+// CHECK:STDOUT:   impl_decl @impl.1 [template] {} {
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc22: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -744,7 +744,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FNotFunction {
-// CHECK:STDOUT:   impl_decl @impl.2 {} {
+// CHECK:STDOUT:   impl_decl @impl.2 [template] {} {
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc35: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -756,7 +756,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: class @F.16;
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FAlias {
-// CHECK:STDOUT:   impl_decl @impl.3 {} {
+// CHECK:STDOUT:   impl_decl @impl.3 [template] {} {
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc51: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -766,7 +766,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FExtraParam {
-// CHECK:STDOUT:   impl_decl @impl.4 {} {
+// CHECK:STDOUT:   impl_decl @impl.4 [template] {} {
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc64: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -776,7 +776,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FExtraImplicitParam {
-// CHECK:STDOUT:   impl_decl @impl.5 {} {
+// CHECK:STDOUT:   impl_decl @impl.5 [template] {} {
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc77: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -786,7 +786,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FExtraReturnType {
-// CHECK:STDOUT:   impl_decl @impl.6 {} {
+// CHECK:STDOUT:   impl_decl @impl.6 [template] {} {
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc91: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -796,7 +796,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FMissingParam {
-// CHECK:STDOUT:   impl_decl @impl.7 {} {
+// CHECK:STDOUT:   impl_decl @impl.7 [template] {} {
 // CHECK:STDOUT:     %J.ref: type = name_ref J, file.%J.decl [template = constants.%.7]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc106: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -806,7 +806,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FMissingImplicitParam {
-// CHECK:STDOUT:   impl_decl @impl.8 {} {
+// CHECK:STDOUT:   impl_decl @impl.8 [template] {} {
 // CHECK:STDOUT:     %J.ref: type = name_ref J, file.%J.decl [template = constants.%.7]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc119: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -816,7 +816,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FMissingReturnType {
-// CHECK:STDOUT:   impl_decl @impl.9 {} {
+// CHECK:STDOUT:   impl_decl @impl.9 [template] {} {
 // CHECK:STDOUT:     %J.ref: type = name_ref J, file.%J.decl [template = constants.%.7]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc132: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -826,7 +826,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FDifferentParamType {
-// CHECK:STDOUT:   impl_decl @impl.10 {} {
+// CHECK:STDOUT:   impl_decl @impl.10 [template] {} {
 // CHECK:STDOUT:     %J.ref: type = name_ref J, file.%J.decl [template = constants.%.7]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc145: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -836,7 +836,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FDifferentImplicitParamType {
-// CHECK:STDOUT:   impl_decl @impl.11 {} {
+// CHECK:STDOUT:   impl_decl @impl.11 [template] {} {
 // CHECK:STDOUT:     %J.ref: type = name_ref J, file.%J.decl [template = constants.%.7]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc158: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -846,7 +846,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FDifferentReturnType {
-// CHECK:STDOUT:   impl_decl @impl.12 {} {
+// CHECK:STDOUT:   impl_decl @impl.12 [template] {} {
 // CHECK:STDOUT:     %J.ref: type = name_ref J, file.%J.decl [template = constants.%.7]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc171: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -856,7 +856,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @FDifferentParamName {
-// CHECK:STDOUT:   impl_decl @impl.13 {} {
+// CHECK:STDOUT:   impl_decl @impl.13 [template] {} {
 // CHECK:STDOUT:     %J.ref: type = name_ref J, file.%J.decl [template = constants.%.7]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc185: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -866,7 +866,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @SelfNestedBadParam {
-// CHECK:STDOUT:   impl_decl @impl.14 {} {
+// CHECK:STDOUT:   impl_decl @impl.14 [template] {} {
 // CHECK:STDOUT:     %SelfNested.ref: type = name_ref SelfNested, file.%SelfNested.decl [template = constants.%.10]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc202: <witness> = complete_type_witness %.5 [template = constants.%.6]
@@ -876,7 +876,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @SelfNestedBadReturnType {
-// CHECK:STDOUT:   impl_decl @impl.15 {} {
+// CHECK:STDOUT:   impl_decl @impl.15 [template] {} {
 // CHECK:STDOUT:     %SelfNested.ref: type = name_ref SelfNested, file.%SelfNested.decl [template = constants.%.10]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %.loc214: <witness> = complete_type_witness %.5 [template = constants.%.6]

toolchain/check/testdata/impl/fail_impl_bad_interface.carbon

@@ -76,7 +76,7 @@ impl i32 as false {}
 // CHECK:STDOUT:   %.loc21_13.2: %.7 = specific_constant imports.%import_ref.4, @ImplicitAs(type) [template = constants.%.8]
 // CHECK:STDOUT:   %Convert.ref: %.7 = name_ref Convert, %.loc21_13.2 [template = constants.%.8]
 // CHECK:STDOUT:   %.loc21_13.3: type = converted @impl.%.loc21_13, <error> [template = <error>]
-// CHECK:STDOUT:   impl_decl @impl {} {
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
 // CHECK:STDOUT:     %int.make_type_32: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc21_6.1: type = value_of_initializer %int.make_type_32 [template = i32]
 // CHECK:STDOUT:     %.loc21_6.2: type = converted %int.make_type_32, %.loc21_6.1 [template = i32]