swiftlang · egorzhdan · Dec 18, 2025
@@ -7818,6 +7818,20 @@ ClangImporter::getCXXFunctionTemplateSpecialization(SubstitutionMap subst,
   if (!inserted)
     return ConcreteDeclRef(fnIt->second);
 
+  // Before we proceed to import the newly instantiated C++ function, make sure
+  // it gets a unique name in Swift. In particular, it must have a different
+  // name from all the other instantiations of the same function template, to
+  // prevent Swift from incorrectly deduplicating the multiple instantiations,
+  // which would cause a silent miscompile. The naming itself is not important,
+  // since this will only get called from synthesized code. Let's use the
+  // mangled Clang name of this instantiation as the swift_name.
+  std::string mangledNewFn;
+  llvm::raw_string_ostream mangleRawStream(mangledNewFn);
+  mangleRawStream << "__swift_specializedThunk_";
+  getMangledName(mangleRawStream, newFn);
+  newFn->addAttr(clang::SwiftNameAttr::CreateImplicit(newFn->getASTContext(),
+                                                      mangledNewFn));
+
   auto *newDecl = cast_or_null<ValueDecl>(
       decl->getASTContext().getClangModuleLoader()->importDeclDirectly(newFn));
   if (!newDecl)

@@ -189,46 +189,46 @@ func testtFreeFunctionsTemplated(frt : FRTStruct, nonFrt: NonFRTStruct) {
     let frtLocalVar1 : Int = 1;
 
     let frtLocalVar2 = global_templated_function_returning_FRT(frtLocalVar1)
-    // CHECK: function_ref @$sSo39global_templated_function_returning_FRTySo9FRTStructVSiFTo : $@convention(c) (Int) -> FRTStruct
+    // CHECK: function_ref @$sSo84__swift_specializedThunk__Z39global_templated_function_returning_FRTIlEP9FRTStructT_ySo0J0VSiFTo : $@convention(c) (Int) -> FRTStruct
 
     let frtLocalVar3 = global_templated_function_returning_FRT_copy(frtLocalVar1)
-    // CHECK: function_ref @$sSo44global_templated_function_returning_FRT_copyySo9FRTStructVSiFTo : $@convention(c) (Int) -> @owned FRTStruct
+    // CHECK: function_ref @$sSo89__swift_specializedThunk__Z44global_templated_function_returning_FRT_copyIlEP9FRTStructT_ySo0L0VSiFTo : $@convention(c) (Int) -> @owned FRTStruct
 
     let frtLocalVar4 = global_templated_function_returning_FRT_create(frtLocalVar1)
-    // CHECK: function_ref @$sSo46global_templated_function_returning_FRT_createySo9FRTStructVSiFTo : $@convention(c) (Int) -> @owned FRTStruct
+    // CHECK: function_ref @$sSo91__swift_specializedThunk__Z46global_templated_function_returning_FRT_createIlEP9FRTStructT_ySo0L0VSiFTo : $@convention(c) (Int) -> @owned FRTStruct
 
     let frtLocalVar5 = global_templated_function_returning_FRT_init(frtLocalVar1)
-    // CHECK: function_ref @$sSo44global_templated_function_returning_FRT_initySo9FRTStructVSiFTo : $@convention(c) (Int) -> FRTStruct
+    // CHECK: function_ref @$sSo89__swift_specializedThunk__Z44global_templated_function_returning_FRT_initIlEP9FRTStructT_ySo0L0VSiFTo : $@convention(c) (Int) -> FRTStruct
 
     let frtLocalVar6 = global_templated_function_returning_FRT_clone(frtLocalVar1)
-    // CHECK: function_ref @$sSo45global_templated_function_returning_FRT_cloneySo9FRTStructVSiFTo : $@convention(c) (Int) -> FRTStruct
+    // CHECK: function_ref @$sSo90__swift_specializedThunk__Z45global_templated_function_returning_FRT_cloneIlEP9FRTStructT_ySo0L0VSiFTo : $@convention(c) (Int) -> FRTStruct
 
     let frtLocalVar7 = global_templated_function_returning_FRT_with_attr_returns_retained(frtLocalVar1)
-    // CHECK: function_ref @$sSo66global_templated_function_returning_FRT_with_attr_returns_retainedySo9FRTStructVSiFTo : $@convention(c) (Int) -> @owned FRTStruct
+    // CHECK: function_ref @$sSo111__swift_specializedThunk__Z66global_templated_function_returning_FRT_with_attr_returns_retainedIlEP9FRTStructT_ySo0O0VSiFTo : $@convention(c) (Int) -> @owned FRTStruct
 
     let frtLocalVar8 = global_templated_function_returning_FRT_copy_with_attr_returns_retained(frtLocalVar1)
-    // CHECK: function_ref @$sSo71global_templated_function_returning_FRT_copy_with_attr_returns_retainedySo9FRTStructVSiFTo : $@convention(c) (Int) -> @owned FRTStruct
+    // CHECK: function_ref @$sSo116__swift_specializedThunk__Z71global_templated_function_returning_FRT_copy_with_attr_returns_retainedIlEP9FRTStructT_ySo0P0VSiFTo : $@convention(c) (Int) -> @owned FRTStruct
 
     let frtLocalVar9 = global_templated_function_returning_FRT_create_with_attr_returns_retained(frtLocalVar1)
-    // CHECK: function_ref @$sSo73global_templated_function_returning_FRT_create_with_attr_returns_retainedySo9FRTStructVSiFTo : $@convention(c) (Int) -> @owned FRTStruct
+    // CHECK: function_ref @$sSo118__swift_specializedThunk__Z73global_templated_function_returning_FRT_create_with_attr_returns_retainedIlEP9FRTStructT_ySo0P0VSiFTo : $@convention(c) (Int) -> @owned FRTStruct
 
     let frtLocalVar10 = global_templated_function_returning_FRT_with_attr_returns_unretained(frtLocalVar1)
-    // CHECK: function_ref @$sSo68global_templated_function_returning_FRT_with_attr_returns_unretainedySo9FRTStructVSiFTo : $@convention(c) (Int) -> FRTStruct
+    // CHECK: function_ref @$sSo113__swift_specializedThunk__Z68global_templated_function_returning_FRT_with_attr_returns_unretainedIlEP9FRTStructT_ySo0O0VSiFTo : $@convention(c) (Int) -> FRTStruct
 
     let frtLocalVar11 = global_templated_function_returning_FRT_copy_with_attr_returns_unretained(frtLocalVar1)
-    // CHECK: function_ref @$sSo73global_templated_function_returning_FRT_copy_with_attr_returns_unretainedySo9FRTStructVSiFTo : $@convention(c) (Int) -> FRTStruct
+    // CHECK: function_ref @$sSo118__swift_specializedThunk__Z73global_templated_function_returning_FRT_copy_with_attr_returns_unretainedIlEP9FRTStructT_ySo0P0VSiFTo : $@convention(c) (Int) -> FRTStruct
 
     let frtLocalVar12 = global_templated_function_returning_FRT_create_with_attr_returns_unretained(frtLocalVar1)
-    // CHECK: function_ref @$sSo75global_templated_function_returning_FRT_create_with_attr_returns_unretainedySo9FRTStructVSiFTo : $@convention(c) (Int) -> FRTStruct
+    // CHECK: function_ref @$sSo120__swift_specializedThunk__Z75global_templated_function_returning_FRT_create_with_attr_returns_unretainedIlEP9FRTStructT_ySo0P0VSiFTo : $@convention(c) (Int) -> FRTStruct
 
     let frtLocalVar13 = global_function_returning_templated_retrun_frt(frt)
-    // CHECK: function_ref @$sSo46global_function_returning_templated_retrun_frtySo9FRTStructVACFTo : $@convention(c) (FRTStruct) -> FRTStruct
+    // CHECK: function_ref @$sSo93__swift_specializedThunk__Z46global_function_returning_templated_retrun_frtIP9FRTStructET_S2_ySo0K0VACFTo : $@convention(c) (FRTStruct) -> FRTStruct
 
     let frtLocalVar14 = global_function_returning_templated_retrun_frt_owned(frt)
-    // CHECK: function_ref @$sSo52global_function_returning_templated_retrun_frt_ownedySo9FRTStructVACFTo : $@convention(c) (FRTStruct) -> @owned FRTStruct
+    // CHECK: function_ref @$sSo99__swift_specializedThunk__Z52global_function_returning_templated_retrun_frt_ownedIP9FRTStructET_S2_ySo0L0VACFTo : $@convention(c) (FRTStruct) -> @owned FRTStruct
 
     let nonFrtLocalVar1 = global_function_returning_templated_retrun_frt_owned(nonFrt)
-    // CHECK: function_ref @$sSo52global_function_returning_templated_retrun_frt_ownedySo12NonFRTStructVACFTo : $@convention(c) (NonFRTStruct) -> NonFRTStruct
+    // CHECK: function_ref @$sSo102__swift_specializedThunk__Z52global_function_returning_templated_retrun_frt_ownedI12NonFRTStructET_S1_ySo0lM0VACFTo : $@convention(c) (NonFRTStruct) -> NonFRTStruct
 }
 
 func testVirtualMethods(base: Base, derived: Derived) {

@@ -16,7 +16,19 @@ struct Struct {
 };
 
 template <typename T>
-void templateTypeParamNotUsedInSignature() {}
+struct is_bool {
+  constexpr static bool value = false;
+};
+
+template <>
+struct is_bool<bool> {
+  constexpr static bool value = true;
+};
+
+template <typename T>
+bool templateTypeParamNotUsedInSignature() {
+  return is_bool<T>::value;
+}
 
 template <typename T, typename U>
 void multiTemplateTypeParamNotUsedInSignature() {}

@@ -7,16 +7,16 @@ import FunctionTemplates
 // CHECK: bb0(%0 : $Int32):
 // CHECK:   [[IL_ZERO:%.*]] = integer_literal $Builtin.Int32, 0
 // CHECK:   [[ZERO:%.*]] = struct $Int32 ([[IL_ZERO]] : $Builtin.Int32)
-// CHECK:   [[PASS_THROUGH_CONST_FN:%.*]] = function_ref @$sSo16passThroughConstys5Int32VACFTo : $@convention(c) (Int32) -> Int32
+// CHECK:   [[PASS_THROUGH_CONST_FN:%.*]] = function_ref @$sSo54__swift_specializedThunk__Z16passThroughConstIiEKT_S0_ys5Int32VACFTo : $@convention(c) (Int32) -> Int32
 // CHECK:   [[A:%.*]] = apply [[PASS_THROUGH_CONST_FN]]([[ZERO]]) : $@convention(c) (Int32) -> Int32
 
-// CHECK:   [[PASS_THROUGH_FN:%.*]] = function_ref @$sSo11passThroughys5Int32VACFTo : $@convention(c) (Int32) -> Int32
+// CHECK:   [[PASS_THROUGH_FN:%.*]] = function_ref @$sSo48__swift_specializedThunk__Z11passThroughIiET_S0_ys5Int32VACFTo : $@convention(c) (Int32) -> Int32
 // CHECK:   [[B:%.*]] = apply [[PASS_THROUGH_FN]](%0) : $@convention(c) (Int32) -> Int32
 
-// CHECK:   [[ADD_TWO_FN:%.*]] = function_ref @$sSo18addMixedTypeParamsys5Int32VAC_ACtFTo : $@convention(c) (Int32, Int32) -> Int32
+// CHECK:   [[ADD_TWO_FN:%.*]] = function_ref @$sSo59__swift_specializedThunk__Z18addMixedTypeParamsIiiET_S0_T0_ys5Int32VAC_ACtFTo : $@convention(c) (Int32, Int32) -> Int32
 // CHECK:   [[C:%.*]] = apply [[ADD_TWO_FN]]([[A]], [[B]]) : $@convention(c) (Int32, Int32) -> Int32
 
-// CHECK:   [[ADD_FN:%.*]] = function_ref @$sSo17addSameTypeParamsys5Int32VAC_ACtFTo : $@convention(c) (Int32, Int32) -> Int32
+// CHECK:   [[ADD_FN:%.*]] = function_ref @$sSo054__swift_specializedThunk__Z17addSameTypeParamsIiET_S0_J1_ys5Int32VAC_ACtFTo : $@convention(c) (Int32, Int32) -> Int32
 // CHECK:   [[OUT:%.*]] = apply [[ADD_FN]]([[B]], [[C_32:%.*]]) : $@convention(c) (Int32, Int32) -> Int32
 // CHECK:   return [[OUT]] : $Int32
 

@@ -4,16 +4,16 @@ import MemberTemplates
 
 // CHECK-LABEL: sil hidden @$s4main9basicTestyyF : $@convention(thin) () -> ()
 
-// CHECK: [[ADD:%.*]] = function_ref @$sSo18HasMemberTemplatesV17addSameTypeParamsys5Int32VAE_AEtFTo : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
+// CHECK: [[ADD:%.*]] = function_ref @$sSo18HasMemberTemplatesV030__swift_specializedThunk__ZN18ab37Templates17addSameTypeParamsIiEET_S1_N1_ys5Int32VAE_AEtFTo : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
 // CHECK: apply [[ADD]]({{.*}}) : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
 
-// CHECK: [[ADD_TWO_TEMPLATES:%.*]] = function_ref @$sSo18HasMemberTemplatesV18addMixedTypeParamsys5Int32VAE_AEtFTo : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
+// CHECK: [[ADD_TWO_TEMPLATES:%.*]] = function_ref @$sSo18HasMemberTemplatesV030__swift_specializedThunk__ZN18aB42Templates18addMixedTypeParamsIiiEET_S1_T0_ys5Int32VAE_AEtFTo : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
 // CHECK: apply [[ADD_TWO_TEMPLATES]]({{.*}}) : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
 
-// CHECK: [[ADD_ALL:%.*]] = function_ref @$sSo18HasMemberTemplatesV6addAllys5Int32VAE_A2EtFTo : $@convention(cxx_method) (Int32, Int32, Int32, @inout HasMemberTemplates) -> Int32
+// CHECK: [[ADD_ALL:%.*]] = function_ref @$sSo18HasMemberTemplatesV030__swift_specializedThunk__ZN18aB28Templates6addAllIiiEEiiT_T0_ys5Int32VAE_A2EtFTo : $@convention(cxx_method) (Int32, Int32, Int32, @inout HasMemberTemplates) -> Int32
 // CHECK: apply [[ADD_ALL]]({{.*}}) : $@convention(cxx_method) (Int32, Int32, Int32, @inout HasMemberTemplates) -> Int32
 
-// CHECK: [[DO_NOTHING:%.*]] = function_ref @$sSo18HasMemberTemplatesV17doNothingConstRefyys5Int32VFTo : $@convention(cxx_method) (@in_guaranteed Int32, @inout HasMemberTemplates) -> ()
+// CHECK: [[DO_NOTHING:%.*]] = function_ref @$sSo18HasMemberTemplatesV030__swift_specializedThunk__ZN18aB37Templates17doNothingConstRefIiEEvRKT_yys5Int32VFTo : $@convention(cxx_method) (@in_guaranteed Int32, @inout HasMemberTemplates) -> ()
 // CHECK: apply [[DO_NOTHING]]({{.*}}) : $@convention(cxx_method) (@in_guaranteed Int32, @inout HasMemberTemplates) -> ()
 
 // CHECK-LABEL: end sil function '$s4main9basicTestyyF'
@@ -26,17 +26,17 @@ func basicTest() {
   obj.doNothingConstRef(i)
 }
 
-// CHECK-LABEL: sil [asmname "{{.*}}addSameTypeParams{{.*}}"] [clang HasMemberTemplates.addSameTypeParams] @$sSo18HasMemberTemplatesV17addSameTypeParamsys5Int32VAE_AEtFTo : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
+// CHECK-LABEL: sil [asmname "{{.*}}addSameTypeParams{{.*}}"] [clang HasMemberTemplates.__swift_specializedThunk__ZN18HasMemberTemplates17addSameTypeParamsIiEET_S1_S1_] @$sSo18HasMemberTemplatesV030__swift_specializedThunk__ZN18ab37Templates17addSameTypeParamsIiEET_S1_N1_ys5Int32VAE_AEtFTo : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
 
-// CHECK-LABEL: sil [asmname "{{.*}}addMixedTypeParams{{.*}}"] [clang HasMemberTemplates.addMixedTypeParams] @$sSo18HasMemberTemplatesV18addMixedTypeParamsys5Int32VAE_AEtFTo : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
+// CHECK-LABEL: sil [asmname "{{.*}}addMixedTypeParams{{.*}}"] [clang HasMemberTemplates.__swift_specializedThunk__ZN18HasMemberTemplates18addMixedTypeParamsIiiEET_S1_T0_] @$sSo18HasMemberTemplatesV030__swift_specializedThunk__ZN18aB42Templates18addMixedTypeParamsIiiEET_S1_T0_ys5Int32VAE_AEtFTo : $@convention(cxx_method) (Int32, Int32, @inout HasMemberTemplates) -> Int32
 
-// CHECK-LABEL: sil [asmname "{{.*}}addAll{{.*}}"] [clang HasMemberTemplates.addAll] @$sSo18HasMemberTemplatesV6addAllys5Int32VAE_A2EtFTo : $@convention(cxx_method) (Int32, Int32, Int32, @inout HasMemberTemplates) -> Int32
+// CHECK-LABEL: sil [asmname "{{.*}}addAll{{.*}}"] [clang HasMemberTemplates.__swift_specializedThunk__ZN18HasMemberTemplates6addAllIiiEEiiT_T0_] @$sSo18HasMemberTemplatesV030__swift_specializedThunk__ZN18aB28Templates6addAllIiiEEiiT_T0_ys5Int32VAE_A2EtFTo : $@convention(cxx_method) (Int32, Int32, Int32, @inout HasMemberTemplates) -> Int32
 
-// CHECK-LABEL: sil [asmname "{{.*}}doNothingConstRef{{.*}}"] [clang HasMemberTemplates.doNothingConstRef] @$sSo18HasMemberTemplatesV17doNothingConstRefyys5Int32VFTo : $@convention(cxx_method) (@in_guaranteed Int32, @inout HasMemberTemplates) -> ()
+// CHECK-LABEL: sil [asmname "{{.*}}doNothingConstRef{{.*}}"] [clang HasMemberTemplates.__swift_specializedThunk__ZN18HasMemberTemplates17doNothingConstRefIiEEvRKT_] @$sSo18HasMemberTemplatesV030__swift_specializedThunk__ZN18aB37Templates17doNothingConstRefIiEEvRKT_yys5Int32VFTo : $@convention(cxx_method) (@in_guaranteed Int32, @inout HasMemberTemplates) -> ()
 
 // CHECK-LABEL: sil hidden @$s4main12testSetValueyyF : $@convention(thin) () -> ()
 
-// CHECK: [[SET_VALUE:%.*]] = function_ref @$sSo0044TemplateClassWithMemberTemplatesCInt_CeCInkcV8setValueyySiFTo : $@convention(cxx_method) (Int, @inout TemplateClassWithMemberTemplates<CInt>) -> ()
+// CHECK: [[SET_VALUE:%.*]] = function_ref @$sSo0044TemplateClassWithMemberTemplatesCInt_CeCInkcV81__swift_specializedThunk__ZN32TemplateClassWithMemberTemplatesIiE8setValueIlEEvT_yySiFTo : $@convention(cxx_method) (Int, @inout TemplateClassWithMemberTemplates<CInt>) -> ()
 // CHECK: apply [[SET_VALUE]]({{.*}}) : $@convention(cxx_method) (Int, @inout TemplateClassWithMemberTemplates<CInt>) -> ()
 
 // CHECK-LABEL: end sil function '$s4main12testSetValueyyF'
@@ -47,13 +47,13 @@ func testSetValue() {
 
 // CHECK-LABEL: sil hidden @$s4main17testStaticMembersyyF : $@convention(thin) () -> ()
 
-// CHECK: [[ADD_FN:%.*]] = function_ref @$sSo24HasStaticMemberTemplatesV3addyS2i_SitFZTo : $@convention(c) (Int, Int) -> Int
+// CHECK: [[ADD_FN:%.*]] = function_ref @$sSo24HasStaticMemberTemplatesV030__swift_specializedThunk__ZN24abc22Templates3addIlEET_S1_L1_yS2i_SitFZTo : $@convention(c) (Int, Int) -> Int
 // CHECK: apply [[ADD_FN]]({{.*}}) : $@convention(c) (Int, Int) -> Int
 
-// CHECK: [[ADD_TWO_TEMPLATES_FN:%.*]] = function_ref @$sSo24HasStaticMemberTemplatesV06addTwoD0yS2i_s4Int8VtFZTo : $@convention(c) (Int, Int8) -> Int
+// CHECK: [[ADD_TWO_TEMPLATES_FN:%.*]] = function_ref @$sSo24HasStaticMemberTemplatesV030__swift_specializedThunk__ZN24abc17Templates15addTwoD13IlcEET_S1_T0_yS2i_s4Int8VtFZTo : $@convention(c) (Int, Int8) -> Int
 // CHECK: apply [[ADD_TWO_TEMPLATES_FN]]({{.*}}) : $@convention(c) (Int, Int8) -> Int
 
-// CHECK: [[REMOVE_REFERENCE_FN:%.*]] = function_ref @$sSo24HasStaticMemberTemplatesV15removeReferenceyS2izFZTo : $@convention(c) (@inout Int) -> Int
+// CHECK: [[REMOVE_REFERENCE_FN:%.*]] = function_ref @$sSo24HasStaticMemberTemplatesV030__swift_specializedThunk__ZN24abC36Templates15removeReferenceIlEET_RS1_yS2izFZTo : $@convention(c) (@inout Int) -> Int
 // CHECK: apply [[REMOVE_REFERENCE_FN]]({{.*}}) : $@convention(c) (@inout Int) -> Int
 
 // CHECK-LABEL: end sil function '$s4main17testStaticMembersyyF'
@@ -65,8 +65,8 @@ func testStaticMembers() {
   HasStaticMemberTemplates.removeReference(&x)
 }
 
-// CHECK: sil hidden_external [asmname "{{.*}}add{{.*}}"] [clang HasStaticMemberTemplates.add] @$sSo24HasStaticMemberTemplatesV3addyS2i_SitFZTo : $@convention(c) (Int, Int) -> Int
+// CHECK: sil hidden_external [asmname "{{.*}}add{{.*}}"] [clang HasStaticMemberTemplates.__swift_specializedThunk__ZN24HasStaticMemberTemplates3addIlEET_S1_S1_] @$sSo24HasStaticMemberTemplatesV030__swift_specializedThunk__ZN24abc22Templates3addIlEET_S1_L1_yS2i_SitFZTo : $@convention(c) (Int, Int) -> Int
 
-// CHECK: sil hidden_external [asmname "{{.*}}addTwoTemplates{{.*}}"] [clang HasStaticMemberTemplates.addTwoTemplates] @$sSo24HasStaticMemberTemplatesV06addTwoD0yS2i_s4Int8VtFZTo : $@convention(c) (Int, Int8) -> Int
+// CHECK: sil hidden_external [asmname "{{.*}}addTwoTemplates{{.*}}"] [clang HasStaticMemberTemplates.__swift_specializedThunk__ZN24HasStaticMemberTemplates15addTwoTemplatesIlcEET_S1_T0_] @$sSo24HasStaticMemberTemplatesV030__swift_specializedThunk__ZN24abc17Templates15addTwoD13IlcEET_S1_T0_yS2i_s4Int8VtFZTo : $@convention(c) (Int, Int8) -> Int
 
-// CHECK: sil hidden_external [asmname "{{.*}}removeReference{{.*}}"] [clang HasStaticMemberTemplates.removeReference] @$sSo24HasStaticMemberTemplatesV15removeReferenceyS2izFZTo : $@convention(c) (@inout Int) -> Int
+// CHECK: sil hidden_external [asmname "{{.*}}removeReference{{.*}}"] [clang HasStaticMemberTemplates.__swift_specializedThunk__ZN24HasStaticMemberTemplates15removeReferenceIlEET_RS1_] @$sSo24HasStaticMemberTemplatesV030__swift_specializedThunk__ZN24abC36Templates15removeReferenceIlEET_RS1_yS2izFZTo : $@convention(c) (@inout Int) -> Int
@@ -0,0 +1,17 @@
+// RUN: %target-swift-emit-silgen %s -cxx-interoperability-mode=default -I %S/Inputs | %FileCheck %s
+
+import TemplateTypeParameterNotInSignature
+
+_ = templateTypeParamNotUsedInSignature(T: Int.self)
+_ = templateTypeParamNotUsedInSignature(T: Bool.self)
+
+
+// CHECK: sil [transparent] [serialized] [ossa] @$sSC35templateTypeParamNotUsedInSignatureySbSimF : $@convention(thin) (@thin Int.Type) -> Bool {
+// CHECK: bb0(%0 : $@thin Int.Type):
+// CHECK:   {{.*}} = function_ref @$sSo69__swift_specializedThunk__Z35templateTypeParamNotUsedInSignatureIlEbvSbyFTo : $@convention(c) () -> Bool
+// CHECK: } // end sil function '$sSC35templateTypeParamNotUsedInSignatureySbSimF'
+
+// CHECK: sil [transparent] [serialized] [ossa] @$sSC35templateTypeParamNotUsedInSignatureyS2bmF : $@convention(thin) (@thin Bool.Type) -> Bool {
+// CHECK: bb0(%0 : $@thin Bool.Type):
+// CHECK:   {{.*}} = function_ref @$sSo69__swift_specializedThunk__Z35templateTypeParamNotUsedInSignatureIbEbvSbyFTo : $@convention(c) () -> Bool
+// CHECK: } // end sil function '$sSC35templateTypeParamNotUsedInSignatureyS2bmF'
@@ -19,8 +19,12 @@ TemplateNotInSignatureTestSuite.test("Function with defaulted template type para
 
 TemplateNotInSignatureTestSuite.test("Instantiate the same function template twice.") {
   // Intentionally test the same thing twice.
-  templateTypeParamNotUsedInSignature(T: Int.self)
-  templateTypeParamNotUsedInSignature(T: Int.self)
+  let res1 = templateTypeParamNotUsedInSignature(T: Int.self)
+  expectFalse(res1)
+  let res2 = templateTypeParamNotUsedInSignature(T: Int.self)
+  expectFalse(res2)
+  let res3 = templateTypeParamNotUsedInSignature(T: Bool.self)
+  expectTrue(res3)
 }
 
 TemplateNotInSignatureTestSuite.test("Pointer types") {