llvm · mizvekov · Aug 5, 2024 · Oct 23, 2022
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
@@ -148,6 +148,7 @@ Improvements to Clang's diagnostics
 - Clang now diagnoses undefined behavior in constant expressions more consistently. This includes invalid shifts, and signed overflow in arithmetic.
 
 - -Wdangling-assignment-gsl is enabled by default.
+- Clang now does a better job preserving the template arguments as written when specializing concepts.
 
 Improvements to Clang's time-trace
 ----------------------------------

diff --git a/clang/include/clang/Sema/Template.h b/clang/include/clang/Sema/Template.h
@@ -234,7 +234,8 @@ enum class TemplateSubstitutionKind : char {
     /// Replaces the current 'innermost' level with the provided argument list.
     /// This is useful for type deduction cases where we need to get the entire
     /// list from the AST, but then add the deduced innermost list.
-    void replaceInnermostTemplateArguments(Decl *AssociatedDecl, ArgList Args) {
+    void replaceInnermostTemplateArguments(Decl *AssociatedDecl, ArgList Args,
+                                           bool Final = false) {
       assert((!TemplateArgumentLists.empty() || NumRetainedOuterLevels) &&
              "Replacing in an empty list?");
 
@@ -246,8 +247,7 @@ enum class TemplateSubstitutionKind : char {
         TemplateArgumentLists[0].Args = Args;
       } else {
         --NumRetainedOuterLevels;
-        TemplateArgumentLists.push_back(
-            {{AssociatedDecl, /*Final=*/false}, Args});
+        TemplateArgumentLists.push_back({{AssociatedDecl, Final}, Args});
       }
     }
 

diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
@@ -414,7 +414,8 @@ DiagRecursiveConstraintEval(Sema &S, llvm::FoldingSetNodeID &ID,
   E->Profile(ID, S.Context, /*Canonical=*/true);
   for (const auto &List : MLTAL)
     for (const auto &TemplateArg : List.Args)
-      TemplateArg.Profile(ID, S.Context);
+      S.Context.getCanonicalTemplateArgument(TemplateArg)
+          .Profile(ID, S.Context);
 
   // Note that we have to do this with our own collection, because there are
   // times where a constraint-expression check can cause us to need to evaluate
@@ -638,8 +639,8 @@ bool Sema::CheckConstraintSatisfaction(
   // here.
   llvm::SmallVector<TemplateArgument, 4> FlattenedArgs;
   for (auto List : TemplateArgsLists)
-    FlattenedArgs.insert(FlattenedArgs.end(), List.Args.begin(),
-                         List.Args.end());
+    for (const TemplateArgument &Arg : List.Args)
+      FlattenedArgs.emplace_back(Context.getCanonicalTemplateArgument(Arg));
 
   llvm::FoldingSetNodeID ID;
   ConstraintSatisfaction::Profile(ID, Context, Template, FlattenedArgs);
@@ -823,6 +824,8 @@ Sema::SetupConstraintCheckingTemplateArgumentsAndScope(
                                    /*RelativeToPrimary=*/true,
                                    /*Pattern=*/nullptr,
                                    /*ForConstraintInstantiation=*/true);
+  if (TemplateArgs)
+    MLTAL.replaceInnermostTemplateArguments(FD, *TemplateArgs, /*Final=*/true);
   if (SetupConstraintScope(FD, TemplateArgs, MLTAL, Scope))
     return std::nullopt;
 
@@ -1476,7 +1479,7 @@ static bool substituteParameterMappings(Sema &S, NormalizedConstraint &N,
                                         const ConceptSpecializationExpr *CSE) {
   MultiLevelTemplateArgumentList MLTAL = S.getTemplateInstantiationArgs(
       CSE->getNamedConcept(), CSE->getNamedConcept()->getLexicalDeclContext(),
-      /*Final=*/false, CSE->getTemplateArguments(),
+      /*Final=*/true, CSE->getTemplateArguments(),
       /*RelativeToPrimary=*/true,
       /*Pattern=*/nullptr,
       /*ForConstraintInstantiation=*/true);

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
@@ -9330,14 +9330,13 @@ Sema::BuildExprRequirement(
     //     be satisfied.
     TemplateParameterList *TPL =
         ReturnTypeRequirement.getTypeConstraintTemplateParameterList();
-    QualType MatchedType =
-        Context.getReferenceQualifiedType(E).getCanonicalType();
+    QualType MatchedType = Context.getReferenceQualifiedType(E);
     llvm::SmallVector<TemplateArgument, 1> Args;
     Args.push_back(TemplateArgument(MatchedType));
 
     auto *Param = cast<TemplateTypeParmDecl>(TPL->getParam(0));
 
-    MultiLevelTemplateArgumentList MLTAL(Param, Args, /*Final=*/false);
+    MultiLevelTemplateArgumentList MLTAL(Param, Args, /*Final=*/true);
     MLTAL.addOuterRetainedLevels(TPL->getDepth());
     const TypeConstraint *TC = Param->getTypeConstraint();
     assert(TC && "Type Constraint cannot be null here");

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
@@ -4358,13 +4358,13 @@ Sema::CheckConceptTemplateId(const CXXScopeSpec &SS,
 
   auto *CSD = ImplicitConceptSpecializationDecl::Create(
       Context, NamedConcept->getDeclContext(), NamedConcept->getLocation(),
-      CanonicalConverted);
+      SugaredConverted);
   ConstraintSatisfaction Satisfaction;
   bool AreArgsDependent =
       TemplateSpecializationType::anyDependentTemplateArguments(
-          *TemplateArgs, CanonicalConverted);
-  MultiLevelTemplateArgumentList MLTAL(NamedConcept, CanonicalConverted,
-                                       /*Final=*/false);
+          *TemplateArgs, SugaredConverted);
+  MultiLevelTemplateArgumentList MLTAL(NamedConcept, SugaredConverted,
+                                       /*Final=*/true);
   LocalInstantiationScope Scope(*this);
 
   EnterExpressionEvaluationContext EECtx{
@@ -5582,7 +5582,7 @@ bool Sema::CheckTemplateArgumentList(
     CXXThisScopeRAII(*this, RD, ThisQuals, RD != nullptr);
 
     MultiLevelTemplateArgumentList MLTAL = getTemplateInstantiationArgs(
-        Template, NewContext, /*Final=*/false, CanonicalConverted,
+        Template, NewContext, /*Final=*/true, SugaredConverted,
         /*RelativeToPrimary=*/true,
         /*Pattern=*/nullptr,
         /*ForConceptInstantiation=*/true);

diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3078,7 +3078,7 @@ CheckDeducedArgumentConstraints(Sema &S, TemplateDeclT *Template,
   // If we don't need to replace the deduced template arguments,
   // we can add them immediately as the inner-most argument list.
   if (!DeducedArgsNeedReplacement(Template))
-    Innermost = CanonicalDeducedArgs;
+    Innermost = SugaredDeducedArgs;
 
   MultiLevelTemplateArgumentList MLTAL = S.getTemplateInstantiationArgs(
       Template, Template->getDeclContext(), /*Final=*/false, Innermost,
@@ -3090,7 +3090,7 @@ CheckDeducedArgumentConstraints(Sema &S, TemplateDeclT *Template,
   // not class-scope explicit specialization, so replace with Deduced Args
   // instead of adding to inner-most.
   if (!Innermost)
-    MLTAL.replaceInnermostTemplateArguments(Template, CanonicalDeducedArgs);
+    MLTAL.replaceInnermostTemplateArguments(Template, SugaredDeducedArgs);
 
   if (S.CheckConstraintSatisfaction(Template, AssociatedConstraints, MLTAL,
                                     Info.getLocation(),
@@ -3913,13 +3913,13 @@ TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
       (CanonicalBuilder.size() ==
        FunctionTemplate->getTemplateParameters()->size())) {
     if (CheckInstantiatedFunctionTemplateConstraints(
-            Info.getLocation(), Specialization, CanonicalBuilder,
+            Info.getLocation(), Specialization, SugaredBuilder,
             Info.AssociatedConstraintsSatisfaction))
       return TemplateDeductionResult::MiscellaneousDeductionFailure;
 
     if (!Info.AssociatedConstraintsSatisfaction.IsSatisfied) {
-      Info.reset(Info.takeSugared(),
-                 TemplateArgumentList::CreateCopy(Context, CanonicalBuilder));
+      Info.reset(TemplateArgumentList::CreateCopy(Context, SugaredBuilder),
+                 Info.takeCanonical());
       return TemplateDeductionResult::ConstraintsNotSatisfied;
     }
   }
@@ -4993,8 +4993,8 @@ static bool CheckDeducedPlaceholderConstraints(Sema &S, const AutoType &Type,
                                   /*PartialTemplateArgs=*/false,
                                   SugaredConverted, CanonicalConverted))
     return true;
-  MultiLevelTemplateArgumentList MLTAL(Concept, CanonicalConverted,
-                                       /*Final=*/false);
+  MultiLevelTemplateArgumentList MLTAL(Concept, SugaredConverted,
+                                       /*Final=*/true);
   // Build up an EvaluationContext with an ImplicitConceptSpecializationDecl so
   // that the template arguments of the constraint can be preserved. For
   // example:
@@ -5008,7 +5008,7 @@ static bool CheckDeducedPlaceholderConstraints(Sema &S, const AutoType &Type,
       S, Sema::ExpressionEvaluationContext::Unevaluated,
       ImplicitConceptSpecializationDecl::Create(
           S.getASTContext(), Concept->getDeclContext(), Concept->getLocation(),
-          CanonicalConverted));
+          SugaredConverted));
   if (S.CheckConstraintSatisfaction(Concept, {Concept->getConstraintExpr()},
                                     MLTAL, TypeLoc.getLocalSourceRange(),
                                     Satisfaction))

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2391,7 +2391,7 @@ void ASTDeclReader::VisitImplicitConceptSpecializationDecl(
   VisitDecl(D);
   llvm::SmallVector<TemplateArgument, 4> Args;
   for (unsigned I = 0; I < D->NumTemplateArgs; ++I)
-    Args.push_back(Record.readTemplateArgument(/*Canonicalize=*/true));
+    Args.push_back(Record.readTemplateArgument(/*Canonicalize=*/false));
   D->setTemplateArguments(Args);
 }
 

diff --git a/clang/test/AST/ast-dump-concepts.cpp b/clang/test/AST/ast-dump-concepts.cpp
@@ -20,8 +20,9 @@ struct Foo {
   // CHECK:      TemplateTypeParmDecl {{.*}} referenced Concept {{.*}} 'binary_concept'
   // CHECK-NEXT: `-ConceptSpecializationExpr {{.*}} <col:13, col:31> 'bool' Concept {{.*}} 'binary_concept'
   // CHECK-NEXT:   |-ImplicitConceptSpecializationDecl {{.*}} <line:13:9> col:9
-  // CHECK-NEXT:   | |-TemplateArgument type 'type-parameter-1-0'  
-  // CHECK-NEXT:   | | `-TemplateTypeParmType {{.*}} 'type-parameter-1-0' dependent {{.*}}depth 1 index 0
+  // CHECK-NEXT:   | |-TemplateArgument type 'R'
+  // CHECK-NEXT:   | | `-TemplateTypeParmType {{.*}} 'R' dependent {{.*}}depth 1 index 0
+  // CHECK-NEXT:   | |   `-TemplateTypeParm {{.*}} 'R'
   // CHECK-NEXT:   | `-TemplateArgument type 'int'
   // CHECK-NEXT:   |   `-BuiltinType {{.*}} 'int'
   // CHECK-NEXT:   |-TemplateArgument {{.*}} type 'R'
@@ -35,8 +36,9 @@ struct Foo {
   // CHECK:      TemplateTypeParmDecl {{.*}} referenced Concept {{.*}} 'unary_concept'
   // CHECK-NEXT: `-ConceptSpecializationExpr {{.*}} <col:13> 'bool'
   // CHECK-NEXT:   |-ImplicitConceptSpecializationDecl {{.*}} <line:10:9> col:9
-  // CHECK-NEXT:   | `-TemplateArgument type 'type-parameter-1-0'
-  // CHECK-NEXT:   |   `-TemplateTypeParmType {{.*}} 'type-parameter-1-0' dependent {{.*}}depth 1 index 0
+  // CHECK-NEXT:   | `-TemplateArgument type 'R'
+  // CHECK-NEXT:   |   `-TemplateTypeParmType {{.*}} 'R' dependent {{.*}}depth 1 index 0
+  // CHECK-NEXT:   |     `-TemplateTypeParm {{.*}} 'R'
   template <unary_concept R>
   Foo(R);
 

diff --git a/clang/test/CXX/expr/expr.prim/expr.prim.req/compound-requirement.cpp b/clang/test/CXX/expr/expr.prim/expr.prim.req/compound-requirement.cpp
@@ -35,14 +35,14 @@ using r2i2 = r2<A>; // expected-error{{constraints not satisfied for class templ
 using r2i3 = r2<D>;
 using r2i4 = r2<const D>; // expected-error{{constraints not satisfied for class template 'r2' [with T = const D]}}
 
-template<typename T> requires requires { { sizeof(T) }; } // expected-note{{because 'sizeof(T)' would be invalid: invalid application of 'sizeof' to an incomplete type 'void'}} expected-note{{because 'sizeof(T)' would be invalid: invalid application of 'sizeof' to an incomplete type 'nonexistent'}}
+template<typename T> requires requires { { sizeof(T) }; } // expected-note{{because 'sizeof(T)' would be invalid: invalid application of 'sizeof' to an incomplete type 'void'}} expected-note{{because 'sizeof(T)' would be invalid: invalid application of 'sizeof' to an incomplete type 'class nonexistent'}}
 struct r3 {};
 
 using r3i1 = r3<int>;
 using r3i2 = r3<A>;
 using r3i3 = r3<A &>;
 using r3i4 = r3<void>; // expected-error{{constraints not satisfied for class template 'r3' [with T = void]}}
-using r3i4 = r3<class nonexistent>; // expected-error{{constraints not satisfied for class template 'r3' [with T = nonexistent]}}
+using r3i4 = r3<class nonexistent>; // expected-error{{constraints not satisfied for class template 'r3' [with T = class nonexistent]}}
 
 // Non-dependent expressions
 
@@ -149,7 +149,7 @@ namespace std_example {
   template<typename T> constexpr bool is_same_v<T, T> = true;
 
   template<typename T, typename U> concept same_as = is_same_v<T, U>;
-  // expected-note@-1 {{because 'is_same_v<int, int *>' evaluated to false}}
+  // expected-note@-1 {{because 'is_same_v<int, typename T2::inner>' evaluated to false}}
 
   static_assert(C1<int>);
   static_assert(C1<int*>);
@@ -173,9 +173,9 @@ namespace std_example {
     int operator *() { return 0; }
   };
   static_assert(C2<T1>);
-  template<C2 T> struct C2_check {}; // expected-note{{because 'int' does not satisfy 'C2'}} expected-note{{because 'std_example::T2' does not satisfy 'C2'}}
+  template<C2 T> struct C2_check {}; // expected-note{{because 'int' does not satisfy 'C2'}} expected-note{{because 'T2' does not satisfy 'C2'}}
   using c2c1 = C2_check<int>; // expected-error{{constraints not satisfied for class template 'C2_check' [with T = int]}}
-  using c2c2 = C2_check<T2>; // expected-error{{constraints not satisfied for class template 'C2_check' [with T = std_example::T2]}}
+  using c2c2 = C2_check<T2>; // expected-error{{constraints not satisfied for class template 'C2_check' [with T = T2]}}
 
   template<typename T>
   void g(T t) noexcept(sizeof(T) == 1) {}

diff --git a/clang/test/CXX/expr/expr.prim/expr.prim.req/nested-requirement.cpp b/clang/test/CXX/expr/expr.prim/expr.prim.req/nested-requirement.cpp
@@ -27,7 +27,7 @@ using r4i = X<void>::r4<int>; // expected-error{{constraints not satisfied for c
 
 // C++ [expr.prim.req.nested] Examples
 namespace std_example {
-  template<typename U> concept C1 = sizeof(U) == 1; // expected-note{{because 'sizeof(int) == 1' (4 == 1) evaluated to false}}
+  template<typename U> concept C1 = sizeof(U) == 1; // expected-note{{because 'sizeof(decltype(+t)) == 1' (4 == 1) evaluated to false}}
   template<typename T> concept D =
     requires (T t) {
       requires C1<decltype (+t)>; // expected-note{{because 'decltype(+t)' (aka 'int') does not satisfy 'C1'}}

diff --git a/clang/test/CXX/expr/expr.prim/expr.prim.req/simple-requirement.cpp b/clang/test/CXX/expr/expr.prim/expr.prim.req/simple-requirement.cpp
@@ -39,14 +39,14 @@ using r2i4 = r2<const D>; // expected-error{{constraints not satisfied for class
 
 template<typename T> requires requires { sizeof(T); }
 // expected-note@-1{{because 'sizeof(T)' would be invalid: invalid application of 'sizeof' to an incomplete type 'void'}}
-// expected-note@-2{{because 'sizeof(T)' would be invalid: invalid application of 'sizeof' to an incomplete type 'nonexistent'}}
+// expected-note@-2{{because 'sizeof(T)' would be invalid: invalid application of 'sizeof' to an incomplete type 'class nonexistent'}}
 struct r3 {};
 
 using r3i1 = r3<int>;
 using r3i2 = r3<A>;
 using r3i3 = r3<A &>;
 using r3i4 = r3<void>; // expected-error{{constraints not satisfied for class template 'r3' [with T = void]}}
-using r3i4 = r3<class nonexistent>; // expected-error{{constraints not satisfied for class template 'r3' [with T = nonexistent]}}
+using r3i4 = r3<class nonexistent>; // expected-error{{constraints not satisfied for class template 'r3' [with T = class nonexistent]}}
 
 template<typename T> requires requires (T t) { 0; "a"; (void)'a'; }
 struct r4 {};

diff --git a/clang/test/CXX/expr/expr.prim/expr.prim.req/type-requirement.cpp b/clang/test/CXX/expr/expr.prim/expr.prim.req/type-requirement.cpp
@@ -182,14 +182,14 @@ namespace std_example {
   static_assert(C1<has_inner_and_type> && C2<has_inner_and_type> && C3<has_inner_and_type>);
   template<C1 T> struct C1_check {};
   // expected-note@-1 {{because 'int' does not satisfy 'C1'}}
-  // expected-note@-2 {{because 'std_example::has_type' does not satisfy 'C1'}}
+  // expected-note@-2 {{because 'has_type' does not satisfy 'C1'}}
   template<C2 T> struct C2_check {};
-  // expected-note@-1 {{because 'std_example::has_inner' does not satisfy 'C2'}}
+  // expected-note@-1 {{because 'has_inner' does not satisfy 'C2'}}
   template<C3 T> struct C3_check {};
   // expected-note@-1 {{because 'void' does not satisfy 'C3'}}
   using c1 = C1_check<int>; // expected-error{{constraints not satisfied for class template 'C1_check' [with T = int]}}
-  using c2 = C1_check<has_type>; // expected-error{{constraints not satisfied for class template 'C1_check' [with T = std_example::has_type]}}
-  using c3 = C2_check<has_inner>; // expected-error{{constraints not satisfied for class template 'C2_check' [with T = std_example::has_inner]}}
+  using c2 = C1_check<has_type>; // expected-error{{constraints not satisfied for class template 'C1_check' [with T = has_type]}}
+  using c3 = C2_check<has_inner>; // expected-error{{constraints not satisfied for class template 'C2_check' [with T = has_inner]}}
   using c4 = C3_check<void>; // expected-error{{constraints not satisfied for class template 'C3_check' [with T = void]}}
 }
 
@@ -199,10 +199,10 @@ template <typename T> concept C = requires { requires requires { T::a; }; };
 // expected-note@-1 {{because 'T::a' would be invalid: no member named 'a' in 'PR48656::T1'}}
 
 template <C...> struct A {};
-// expected-note@-1 {{because 'PR48656::T1' does not satisfy 'C'}}
+// expected-note@-1 {{because 'T1' does not satisfy 'C'}}
 
 struct T1 {};
-template struct A<T1>; // expected-error {{constraints not satisfied for class template 'A' [with $0 = <PR48656::T1>]}}
+template struct A<T1>; // expected-error {{constraints not satisfied for class template 'A' [with $0 = <T1>]}}
 
 struct T2 { static constexpr bool a = false; };
 template struct A<T2>;

diff --git a/clang/test/CXX/temp/temp.constr/temp.constr.normal/p1.cpp b/clang/test/CXX/temp/temp.constr/temp.constr.normal/p1.cpp
@@ -8,7 +8,7 @@ template<typename T> requires Bar<T> && true struct S<T> { };
 
 template<typename T> concept True2 = sizeof(T) >= 0;
 template<typename T> concept Foo2 = True2<T*>;
-// expected-error@-1{{'type name' declared as a pointer to a reference of type 'type-parameter-0-0 &'}}
+// expected-error@-1{{'type name' declared as a pointer to a reference of type 'T &'}}
 template<typename T> concept Bar2 = Foo2<T&>;
 // expected-note@-1{{while substituting into concept arguments here; substitution failures not allowed in concept arguments}}
 template<typename T> requires Bar2<T> struct S2 { };

diff --git a/clang/test/CXX/temp/temp.param/p10-2a.cpp b/clang/test/CXX/temp/temp.param/p10-2a.cpp
@@ -94,8 +94,8 @@ concept OneOf = (is_same_v<T, Ts> || ...);
 // expected-note@-5 {{and 'is_same_v<short, char>' evaluated to false}}
 // expected-note@-6 3{{because 'is_same_v<int, char[1]>' evaluated to false}}
 // expected-note@-7 3{{and 'is_same_v<int, char[2]>' evaluated to false}}
-// expected-note@-8 2{{because 'is_same_v<std::nullptr_t, char>' evaluated to false}}
-// expected-note@-9 2{{and 'is_same_v<std::nullptr_t, int>' evaluated to false}}
+// expected-note@-8 2{{because 'is_same_v<decltype(nullptr), char>' evaluated to false}}
+// expected-note@-9 2{{and 'is_same_v<decltype(nullptr), int>' evaluated to false}}
 
 template<OneOf<char[1], char[2]> T, OneOf<int, long, char> U>
 // expected-note@-1 2{{because 'OneOf<char, char[1], char[2]>' evaluated to false}}