1 files changed, 61 insertions, 32 deletions

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 2bf1511..dcf2876 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -9,6 +9,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "TreeTransform.h"
+#include "clang/AST/ASTConcept.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
@@ -1222,8 +1223,9 @@ static ExprResult formImmediatelyDeclaredConstraint(
   if (auto *CD = dyn_cast<ConceptDecl>(NamedConcept)) {
     ImmediatelyDeclaredConstraint = S.CheckConceptTemplateId(
         SS, /*TemplateKWLoc=*/SourceLocation(), NameInfo,
-        /*FoundDecl=*/FoundDecl ? FoundDecl : NamedConcept, CD,
-        &ConstraintArgs);
+        /*FoundDecl=*/FoundDecl ? FoundDecl : CD, CD, &ConstraintArgs,
+        /*DoCheckConstraintSatisfaction=*/
+        !S.inParameterMappingSubstitution());
   }
   // We have a template template parameter
   else {
@@ -4850,13 +4852,11 @@ void Sema::diagnoseMissingTemplateArguments(const CXXScopeSpec &SS,
   diagnoseMissingTemplateArguments(Name, Loc);
 }
 
-ExprResult
-Sema::CheckConceptTemplateId(const CXXScopeSpec &SS,
-                             SourceLocation TemplateKWLoc,
-                             const DeclarationNameInfo &ConceptNameInfo,
-                             NamedDecl *FoundDecl,
-                             ConceptDecl *NamedConcept,
-                             const TemplateArgumentListInfo *TemplateArgs) {
+ExprResult Sema::CheckConceptTemplateId(
+    const CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
+    const DeclarationNameInfo &ConceptNameInfo, NamedDecl *FoundDecl,
+    TemplateDecl *NamedConcept, const TemplateArgumentListInfo *TemplateArgs,
+    bool DoCheckConstraintSatisfaction) {
   assert(NamedConcept && "A concept template id without a template?");
 
   if (NamedConcept->isInvalidDecl())
@@ -4873,33 +4873,48 @@ Sema::CheckConceptTemplateId(const CXXScopeSpec &SS,
 
   DiagnoseUseOfDecl(NamedConcept, ConceptNameInfo.getLoc());
 
+  // There's a bug with CTAI.CanonicalConverted.
+  // If the template argument contains a DependentDecltypeType that includes a
+  // TypeAliasType, and the same written type had occurred previously in the
+  // source, then the DependentDecltypeType would be canonicalized to that
+  // previous type which would mess up the substitution.
+  // FIXME: Reland https://github.com/llvm/llvm-project/pull/101782 properly!
   auto *CSD = ImplicitConceptSpecializationDecl::Create(
       Context, NamedConcept->getDeclContext(), NamedConcept->getLocation(),
-      CTAI.CanonicalConverted);
+      CTAI.SugaredConverted);
   ConstraintSatisfaction Satisfaction;
   bool AreArgsDependent =
       TemplateSpecializationType::anyDependentTemplateArguments(
-          *TemplateArgs, CTAI.CanonicalConverted);
-  MultiLevelTemplateArgumentList MLTAL(NamedConcept, CTAI.CanonicalConverted,
+          *TemplateArgs, CTAI.SugaredConverted);
+  MultiLevelTemplateArgumentList MLTAL(NamedConcept, CTAI.SugaredConverted,
                                        /*Final=*/false);
-  LocalInstantiationScope Scope(*this);
-
-  EnterExpressionEvaluationContext EECtx{
-      *this, ExpressionEvaluationContext::Unevaluated, CSD};
-
-  if (!AreArgsDependent &&
-      CheckConstraintSatisfaction(
-          NamedConcept, AssociatedConstraint(NamedConcept->getConstraintExpr()),
-          MLTAL,
-          SourceRange(SS.isSet() ? SS.getBeginLoc() : ConceptNameInfo.getLoc(),
-                      TemplateArgs->getRAngleLoc()),
-          Satisfaction))
-    return ExprError();
   auto *CL = ConceptReference::Create(
       Context,
       SS.isSet() ? SS.getWithLocInContext(Context) : NestedNameSpecifierLoc{},
       TemplateKWLoc, ConceptNameInfo, FoundDecl, NamedConcept,
       ASTTemplateArgumentListInfo::Create(Context, *TemplateArgs));
+
+  bool Error = false;
+  if (const auto *Concept = dyn_cast<ConceptDecl>(NamedConcept);
+      Concept && Concept->getConstraintExpr() && !AreArgsDependent &&
+      DoCheckConstraintSatisfaction) {
+
+    LocalInstantiationScope Scope(*this);
+
+    EnterExpressionEvaluationContext EECtx{
+        *this, ExpressionEvaluationContext::Unevaluated, CSD};
+
+    Error = CheckConstraintSatisfaction(
+        NamedConcept, AssociatedConstraint(Concept->getConstraintExpr()), MLTAL,
+        SourceRange(SS.isSet() ? SS.getBeginLoc() : ConceptNameInfo.getLoc(),
+                    TemplateArgs->getRAngleLoc()),
+        Satisfaction, CL);
+    Satisfaction.ContainsErrors = Error;
+  }
+
+  if (Error)
+    return ExprError();
+
   return ConceptSpecializationExpr::Create(
       Context, CL, CSD, AreArgsDependent ? nullptr : &Satisfaction);
 }
@@ -5217,10 +5232,11 @@ bool Sema::CheckTemplateTypeArgument(
   }
   default: {
     // We allow instantiating a template with template argument packs when
-    // building deduction guides.
+    // building deduction guides or mapping constraint template parameters.
     if (Arg.getKind() == TemplateArgument::Pack &&
-        CodeSynthesisContexts.back().Kind ==
-            Sema::CodeSynthesisContext::BuildingDeductionGuides) {
+        (CodeSynthesisContexts.back().Kind ==
+             Sema::CodeSynthesisContext::BuildingDeductionGuides ||
+         inParameterMappingSubstitution())) {
       SugaredConverted.push_back(Arg);
       CanonicalConverted.push_back(Arg);
       return false;
@@ -5813,6 +5829,20 @@ bool Sema::CheckTemplateArgumentList(
     TemplateArgumentListInfo &TemplateArgs, const DefaultArguments &DefaultArgs,
     bool PartialTemplateArgs, CheckTemplateArgumentInfo &CTAI,
     bool UpdateArgsWithConversions, bool *ConstraintsNotSatisfied) {
+  return CheckTemplateArgumentList(
+      Template, GetTemplateParameterList(Template), TemplateLoc, TemplateArgs,
+      DefaultArgs, PartialTemplateArgs, CTAI, UpdateArgsWithConversions,
+      ConstraintsNotSatisfied);
+}
+
+/// Check that the given template argument list is well-formed
+/// for specializing the given template.
+bool Sema::CheckTemplateArgumentList(
+    TemplateDecl *Template, TemplateParameterList *Params,
+    SourceLocation TemplateLoc, TemplateArgumentListInfo &TemplateArgs,
+    const DefaultArguments &DefaultArgs, bool PartialTemplateArgs,
+    CheckTemplateArgumentInfo &CTAI, bool UpdateArgsWithConversions,
+    bool *ConstraintsNotSatisfied) {
 
   if (ConstraintsNotSatisfied)
     *ConstraintsNotSatisfied = false;
@@ -5822,8 +5852,6 @@ bool Sema::CheckTemplateArgumentList(
   // template.
   TemplateArgumentListInfo NewArgs = TemplateArgs;
 
-  TemplateParameterList *Params = GetTemplateParameterList(Template);
-
   SourceLocation RAngleLoc = NewArgs.getRAngleLoc();
 
   // C++23 [temp.arg.general]p1:
@@ -6163,11 +6191,12 @@ bool Sema::CheckTemplateArgumentList(
     CXXThisScopeRAII Scope(*this, RD, ThisQuals, RD != nullptr);
 
     MultiLevelTemplateArgumentList MLTAL = getTemplateInstantiationArgs(
-        Template, NewContext, /*Final=*/false, CTAI.CanonicalConverted,
+        Template, NewContext, /*Final=*/true, CTAI.SugaredConverted,
         /*RelativeToPrimary=*/true,
         /*Pattern=*/nullptr,
         /*ForConceptInstantiation=*/true);
-    if (EnsureTemplateArgumentListConstraints(
+    if (!isa<ConceptDecl>(Template) &&
+        EnsureTemplateArgumentListConstraints(
             Template, MLTAL,
             SourceRange(TemplateLoc, TemplateArgs.getRAngleLoc()))) {
       if (ConstraintsNotSatisfied)