[clang] support pack expansions for trailing requires clauses

clang-tools-extra/clangd/refactor/tweaks/ExtractVariable.cpp

@@ -100,9 +100,9 @@ computeReferencedDecls(const clang::Expr *Expr) {
         TraverseLambdaCapture(LExpr, &Capture, Initializer);
       }
 
-      if (clang::Expr *const RequiresClause =
-              LExpr->getTrailingRequiresClause()) {
-        TraverseStmt(RequiresClause);
+      if (const clang::Expr *RequiresClause =
+              LExpr->getTrailingRequiresClause().ConstraintExpr) {
+        TraverseStmt(const_cast<clang::Expr *>(RequiresClause));
       }
 
       for (auto *const TemplateParam : LExpr->getExplicitTemplateParameters())

clang/docs/ReleaseNotes.rst

@@ -373,6 +373,8 @@ Bug Fixes to C++ Support
 - Improved fix for an issue with pack expansions of type constraints, where this
   now also works if the constraint has non-type or template template parameters.
   (#GH131798)
+- Fix crash when evaluating the trailing requires clause of generic lambdas which are part of
+  a pack expansion.
 - Fixes matching of nested template template parameters. (#GH130362)
 - Correctly diagnoses template template paramters which have a pack parameter
   not in the last position.

clang/include/clang/AST/ASTContext.h

@@ -2906,6 +2906,14 @@ class ASTContext : public RefCountedBase<ASTContext> {
   /// that they may be used in declarations of the same template.
   bool isSameTemplateParameter(const NamedDecl *X, const NamedDecl *Y) const;
 
+  /// Determine whether two 'requires' expressions are similar enough that they
+  /// may be used in re-declarations.
+  ///
+  /// Use of 'requires' isn't mandatory, works with constraints expressed in
+  /// other ways too.
+  bool isSameAssociatedConstraint(const AssociatedConstraint &ACX,
+                                  const AssociatedConstraint &ACY) const;
+
   /// Determine whether two 'requires' expressions are similar enough that they
   /// may be used in re-declarations.
   ///

clang/include/clang/AST/ASTNodeTraverser.h

@@ -538,8 +538,8 @@ class ASTNodeTraverser
       for (const auto *Parameter : D->parameters())
         Visit(Parameter);
 
-    if (const Expr *TRC = D->getTrailingRequiresClause())
-      Visit(TRC);
+    if (const AssociatedConstraint &TRC = D->getTrailingRequiresClause())
+      Visit(TRC.ConstraintExpr);
 
     if (Traversal == TK_IgnoreUnlessSpelledInSource && D->isDefaulted())
       return;

clang/include/clang/AST/Decl.h

@@ -81,13 +81,19 @@ enum class ImplicitParamKind;
 // Holds a constraint expression along with a pack expansion index, if
 // expanded.
 struct AssociatedConstraint {
-  const Expr *ConstraintExpr;
-  int ArgumentPackSubstitutionIndex;
+  const Expr *ConstraintExpr = nullptr;
+  int ArgumentPackSubstitutionIndex = -1;
+
+  constexpr AssociatedConstraint() = default;
 
   explicit AssociatedConstraint(const Expr *ConstraintExpr,
                                 int ArgumentPackSubstitutionIndex = -1)
       : ConstraintExpr(ConstraintExpr),
         ArgumentPackSubstitutionIndex(ArgumentPackSubstitutionIndex) {}
+
+  explicit operator bool() const { return ConstraintExpr != nullptr; }
+
+  bool isNull() const { return !operator bool(); }
 };
 
 /// The top declaration context.
@@ -754,7 +760,7 @@ class DeclaratorDecl : public ValueDecl {
   // and constrained function decls.
   struct ExtInfo : public QualifierInfo {
     TypeSourceInfo *TInfo = nullptr;
-    Expr *TrailingRequiresClause = nullptr;
+    AssociatedConstraint TrailingRequiresClause;
   };
 
   llvm::PointerUnion<TypeSourceInfo *, ExtInfo *> DeclInfo;
@@ -823,17 +829,12 @@ class DeclaratorDecl : public ValueDecl {
   /// \brief Get the constraint-expression introduced by the trailing
   /// requires-clause in the function/member declaration, or null if no
   /// requires-clause was provided.
-  Expr *getTrailingRequiresClause() {
-    return hasExtInfo() ? getExtInfo()->TrailingRequiresClause
-                        : nullptr;
-  }
-
-  const Expr *getTrailingRequiresClause() const {
-    return hasExtInfo() ? getExtInfo()->TrailingRequiresClause
-                        : nullptr;
+  const AssociatedConstraint &getTrailingRequiresClause() const {
+    static constexpr AssociatedConstraint Null;
+    return hasExtInfo() ? getExtInfo()->TrailingRequiresClause : Null;
   }
 
-  void setTrailingRequiresClause(Expr *TrailingRequiresClause);
+  void setTrailingRequiresClause(const AssociatedConstraint &AC);
 
   unsigned getNumTemplateParameterLists() const {
     return hasExtInfo() ? getExtInfo()->NumTemplParamLists : 0;
@@ -2102,7 +2103,7 @@ class FunctionDecl : public DeclaratorDecl,
                const DeclarationNameInfo &NameInfo, QualType T,
                TypeSourceInfo *TInfo, StorageClass S, bool UsesFPIntrin,
                bool isInlineSpecified, ConstexprSpecKind ConstexprKind,
-               Expr *TrailingRequiresClause = nullptr);
+               const AssociatedConstraint &TrailingRequiresClause);
 
   using redeclarable_base = Redeclarable<FunctionDecl>;
 
@@ -2138,7 +2139,7 @@ class FunctionDecl : public DeclaratorDecl,
          TypeSourceInfo *TInfo, StorageClass SC, bool UsesFPIntrin = false,
          bool isInlineSpecified = false, bool hasWrittenPrototype = true,
          ConstexprSpecKind ConstexprKind = ConstexprSpecKind::Unspecified,
-         Expr *TrailingRequiresClause = nullptr) {
+         const AssociatedConstraint &TrailingRequiresClause = {}) {
     DeclarationNameInfo NameInfo(N, NLoc);
     return FunctionDecl::Create(C, DC, StartLoc, NameInfo, T, TInfo, SC,
                                 UsesFPIntrin, isInlineSpecified,
@@ -2151,7 +2152,7 @@ class FunctionDecl : public DeclaratorDecl,
          const DeclarationNameInfo &NameInfo, QualType T, TypeSourceInfo *TInfo,
          StorageClass SC, bool UsesFPIntrin, bool isInlineSpecified,
          bool hasWrittenPrototype, ConstexprSpecKind ConstexprKind,
-         Expr *TrailingRequiresClause);
+         const AssociatedConstraint &TrailingRequiresClause);
 
   static FunctionDecl *CreateDeserialized(ASTContext &C, GlobalDeclID ID);
 
@@ -2644,9 +2645,9 @@ class FunctionDecl : public DeclaratorDecl,
   /// Use this instead of getTrailingRequiresClause for concepts APIs that
   /// accept an ArrayRef of constraint expressions.
   void
-  getAssociatedConstraints(SmallVectorImpl<AssociatedConstraint> &AC) const {
-    if (auto *TRC = getTrailingRequiresClause())
-      AC.emplace_back(TRC);
+  getAssociatedConstraints(SmallVectorImpl<AssociatedConstraint> &ACs) const {
+    if (const AssociatedConstraint &AC = getTrailingRequiresClause())
+      ACs.emplace_back(AC);
   }
 
   /// Get the message that indicates why this function was deleted.

clang/include/clang/AST/DeclCXX.h

@@ -1974,7 +1974,7 @@ class CXXDeductionGuideDecl : public FunctionDecl {
                         const DeclarationNameInfo &NameInfo, QualType T,
                         TypeSourceInfo *TInfo, SourceLocation EndLocation,
                         CXXConstructorDecl *Ctor, DeductionCandidate Kind,
-                        Expr *TrailingRequiresClause,
+                        const AssociatedConstraint &TrailingRequiresClause,
                         const CXXDeductionGuideDecl *GeneratedFrom,
                         SourceDeductionGuideKind SourceKind)
       : FunctionDecl(CXXDeductionGuide, C, DC, StartLoc, NameInfo, T, TInfo,
@@ -2007,7 +2007,7 @@ class CXXDeductionGuideDecl : public FunctionDecl {
          TypeSourceInfo *TInfo, SourceLocation EndLocation,
          CXXConstructorDecl *Ctor = nullptr,
          DeductionCandidate Kind = DeductionCandidate::Normal,
-         Expr *TrailingRequiresClause = nullptr,
+         const AssociatedConstraint &TrailingRequiresClause = {},
          const CXXDeductionGuideDecl *SourceDG = nullptr,
          SourceDeductionGuideKind SK = SourceDeductionGuideKind::None);
 
@@ -2115,7 +2115,7 @@ class CXXMethodDecl : public FunctionDecl {
                 QualType T, TypeSourceInfo *TInfo, StorageClass SC,
                 bool UsesFPIntrin, bool isInline,
                 ConstexprSpecKind ConstexprKind, SourceLocation EndLocation,
-                Expr *TrailingRequiresClause = nullptr)
+                const AssociatedConstraint &TrailingRequiresClause = {})
       : FunctionDecl(DK, C, RD, StartLoc, NameInfo, T, TInfo, SC, UsesFPIntrin,
                      isInline, ConstexprKind, TrailingRequiresClause) {
     if (EndLocation.isValid())
@@ -2128,7 +2128,7 @@ class CXXMethodDecl : public FunctionDecl {
          const DeclarationNameInfo &NameInfo, QualType T, TypeSourceInfo *TInfo,
          StorageClass SC, bool UsesFPIntrin, bool isInline,
          ConstexprSpecKind ConstexprKind, SourceLocation EndLocation,
-         Expr *TrailingRequiresClause = nullptr);
+         const AssociatedConstraint &TrailingRequiresClause = {});
 
   static CXXMethodDecl *CreateDeserialized(ASTContext &C, GlobalDeclID ID);
 
@@ -2596,7 +2596,7 @@ class CXXConstructorDecl final
                      bool UsesFPIntrin, bool isInline,
                      bool isImplicitlyDeclared, ConstexprSpecKind ConstexprKind,
                      InheritedConstructor Inherited,
-                     Expr *TrailingRequiresClause);
+                     const AssociatedConstraint &TrailingRequiresClause);
 
   void anchor() override;
 
@@ -2639,7 +2639,7 @@ class CXXConstructorDecl final
          ExplicitSpecifier ES, bool UsesFPIntrin, bool isInline,
          bool isImplicitlyDeclared, ConstexprSpecKind ConstexprKind,
          InheritedConstructor Inherited = InheritedConstructor(),
-         Expr *TrailingRequiresClause = nullptr);
+         const AssociatedConstraint &TrailingRequiresClause = {});
 
   void setExplicitSpecifier(ExplicitSpecifier ES) {
     assert((!ES.getExpr() ||
@@ -2858,7 +2858,7 @@ class CXXDestructorDecl : public CXXMethodDecl {
                     const DeclarationNameInfo &NameInfo, QualType T,
                     TypeSourceInfo *TInfo, bool UsesFPIntrin, bool isInline,
                     bool isImplicitlyDeclared, ConstexprSpecKind ConstexprKind,
-                    Expr *TrailingRequiresClause = nullptr)
+                    const AssociatedConstraint &TrailingRequiresClause = {})
       : CXXMethodDecl(CXXDestructor, C, RD, StartLoc, NameInfo, T, TInfo,
                       SC_None, UsesFPIntrin, isInline, ConstexprKind,
                       SourceLocation(), TrailingRequiresClause) {
@@ -2873,7 +2873,7 @@ class CXXDestructorDecl : public CXXMethodDecl {
          const DeclarationNameInfo &NameInfo, QualType T, TypeSourceInfo *TInfo,
          bool UsesFPIntrin, bool isInline, bool isImplicitlyDeclared,
          ConstexprSpecKind ConstexprKind,
-         Expr *TrailingRequiresClause = nullptr);
+         const AssociatedConstraint &TrailingRequiresClause = {});
   static CXXDestructorDecl *CreateDeserialized(ASTContext &C, GlobalDeclID ID);
 
   void setOperatorDelete(FunctionDecl *OD, Expr *ThisArg);
@@ -2919,7 +2919,7 @@ class CXXConversionDecl : public CXXMethodDecl {
                     TypeSourceInfo *TInfo, bool UsesFPIntrin, bool isInline,
                     ExplicitSpecifier ES, ConstexprSpecKind ConstexprKind,
                     SourceLocation EndLocation,
-                    Expr *TrailingRequiresClause = nullptr)
+                    const AssociatedConstraint &TrailingRequiresClause = {})
       : CXXMethodDecl(CXXConversion, C, RD, StartLoc, NameInfo, T, TInfo,
                       SC_None, UsesFPIntrin, isInline, ConstexprKind,
                       EndLocation, TrailingRequiresClause),
@@ -2937,7 +2937,7 @@ class CXXConversionDecl : public CXXMethodDecl {
          const DeclarationNameInfo &NameInfo, QualType T, TypeSourceInfo *TInfo,
          bool UsesFPIntrin, bool isInline, ExplicitSpecifier ES,
          ConstexprSpecKind ConstexprKind, SourceLocation EndLocation,
-         Expr *TrailingRequiresClause = nullptr);
+         const AssociatedConstraint &TrailingRequiresClause = {});
   static CXXConversionDecl *CreateDeserialized(ASTContext &C, GlobalDeclID ID);
 
   ExplicitSpecifier getExplicitSpecifier() {

clang/include/clang/AST/ExprCXX.h

@@ -2129,7 +2129,7 @@ class LambdaExpr final : public Expr,
   ArrayRef<NamedDecl *> getExplicitTemplateParameters() const;
 
   /// Get the trailing requires clause, if any.
-  Expr *getTrailingRequiresClause() const;
+  const AssociatedConstraint &getTrailingRequiresClause() const;
 
   /// Whether this is a generic lambda.
   bool isGenericLambda() const { return getTemplateParameterList(); }

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -2253,8 +2253,10 @@ bool RecursiveASTVisitor<Derived>::TraverseFunctionHelper(FunctionDecl *D) {
   }
 
   // Visit the trailing requires clause, if any.
-  if (Expr *TrailingRequiresClause = D->getTrailingRequiresClause()) {
-    TRY_TO(TraverseStmt(TrailingRequiresClause));
+  if (const AssociatedConstraint &TrailingRequiresClause =
+          D->getTrailingRequiresClause()) {
+    TRY_TO(TraverseStmt(
+        const_cast<Expr *>(TrailingRequiresClause.ConstraintExpr)));
   }
 
   if (CXXConstructorDecl *Ctor = dyn_cast<CXXConstructorDecl>(D)) {
@@ -2768,7 +2770,8 @@ DEF_TRAVERSE_STMT(LambdaExpr, {
 
     if (S->hasExplicitResultType())
       TRY_TO(TraverseTypeLoc(Proto.getReturnLoc()));
-    TRY_TO_TRAVERSE_OR_ENQUEUE_STMT(S->getTrailingRequiresClause());
+    TRY_TO_TRAVERSE_OR_ENQUEUE_STMT(
+        const_cast<Expr *>(S->getTrailingRequiresClause().ConstraintExpr));
 
     TRY_TO_TRAVERSE_OR_ENQUEUE_STMT(S->getBody());
   }

clang/include/clang/Sema/Sema.h

@@ -8866,12 +8866,14 @@ class Sema final : public SemaBase {
       CXXMethodDecl *CallOperator, CXXRecordDecl *Class,
       TemplateParameterList *TemplateParams);
 
-  void CompleteLambdaCallOperator(
-      CXXMethodDecl *Method, SourceLocation LambdaLoc,
-      SourceLocation CallOperatorLoc, Expr *TrailingRequiresClause,
-      TypeSourceInfo *MethodTyInfo, ConstexprSpecKind ConstexprKind,
-      StorageClass SC, ArrayRef<ParmVarDecl *> Params,
-      bool HasExplicitResultType);
+  void
+  CompleteLambdaCallOperator(CXXMethodDecl *Method, SourceLocation LambdaLoc,
+                             SourceLocation CallOperatorLoc,
+                             const AssociatedConstraint &TrailingRequiresClause,
+                             TypeSourceInfo *MethodTyInfo,
+                             ConstexprSpecKind ConstexprKind, StorageClass SC,
+                             ArrayRef<ParmVarDecl *> Params,
+                             bool HasExplicitResultType);
 
   /// Returns true if the explicit object parameter was invalid.
   bool DiagnoseInvalidExplicitObjectParameterInLambda(CXXMethodDecl *Method,

clang/lib/AST/ASTContext.cpp

@@ -7070,6 +7070,15 @@ bool ASTContext::hasSameTemplateName(const TemplateName &X,
          getCanonicalTemplateName(Y, IgnoreDeduced);
 }
 
+bool ASTContext::isSameAssociatedConstraint(
+    const AssociatedConstraint &ACX, const AssociatedConstraint &ACY) const {
+  if (ACX.ArgumentPackSubstitutionIndex != ACY.ArgumentPackSubstitutionIndex)
+    return false;
+  if (!isSameConstraintExpr(ACX.ConstraintExpr, ACY.ConstraintExpr))
+    return false;
+  return true;
+}
+
 bool ASTContext::isSameConstraintExpr(const Expr *XCE, const Expr *YCE) const {
   if (!XCE != !YCE)
     return false;
@@ -7386,8 +7395,8 @@ bool ASTContext::isSameEntity(const NamedDecl *X, const NamedDecl *Y) const {
       return false;
     }
 
-    if (!isSameConstraintExpr(FuncX->getTrailingRequiresClause(),
-                              FuncY->getTrailingRequiresClause()))
+    if (!isSameAssociatedConstraint(FuncX->getTrailingRequiresClause(),
+                                    FuncY->getTrailingRequiresClause()))
       return false;
 
     auto GetTypeAsWritten = [](const FunctionDecl *FD) {

clang/lib/AST/ASTImporter.cpp

@@ -3915,8 +3915,9 @@ ExpectedDecl ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
   auto ToEndLoc = importChecked(Err, D->getEndLoc());
   auto ToDefaultLoc = importChecked(Err, D->getDefaultLoc());
   auto ToQualifierLoc = importChecked(Err, D->getQualifierLoc());
-  auto TrailingRequiresClause =
-      importChecked(Err, D->getTrailingRequiresClause());
+  AssociatedConstraint TrailingRequiresClause = D->getTrailingRequiresClause();
+  TrailingRequiresClause.ConstraintExpr =
+      importChecked(Err, TrailingRequiresClause.ConstraintExpr);
   if (Err)
     return std::move(Err);
 

clang/lib/AST/Decl.cpp

@@ -2009,8 +2009,8 @@ void DeclaratorDecl::setQualifierInfo(NestedNameSpecifierLoc QualifierLoc) {
   }
 }
 
-void DeclaratorDecl::setTrailingRequiresClause(Expr *TrailingRequiresClause) {
-  assert(TrailingRequiresClause);
+void DeclaratorDecl::setTrailingRequiresClause(const AssociatedConstraint &AC) {
+  assert(AC);
   // Make sure the extended decl info is allocated.
   if (!hasExtInfo()) {
     // Save (non-extended) type source info pointer.
@@ -2021,7 +2021,7 @@ void DeclaratorDecl::setTrailingRequiresClause(Expr *TrailingRequiresClause) {
     getExtInfo()->TInfo = savedTInfo;
   }
   // Set requires clause info.
-  getExtInfo()->TrailingRequiresClause = TrailingRequiresClause;
+  getExtInfo()->TrailingRequiresClause = AC;
 }
 
 void DeclaratorDecl::setTemplateParameterListsInfo(
@@ -3047,7 +3047,7 @@ FunctionDecl::FunctionDecl(Kind DK, ASTContext &C, DeclContext *DC,
                            TypeSourceInfo *TInfo, StorageClass S,
                            bool UsesFPIntrin, bool isInlineSpecified,
                            ConstexprSpecKind ConstexprKind,
-                           Expr *TrailingRequiresClause)
+                           const AssociatedConstraint &TrailingRequiresClause)
     : DeclaratorDecl(DK, DC, NameInfo.getLoc(), NameInfo.getName(), T, TInfo,
                      StartLoc),
       DeclContext(DK), redeclarable_base(C), Body(), ODRHash(0),
@@ -3571,7 +3571,7 @@ bool FunctionDecl::isMemberLikeConstrainedFriend() const {
     // If these friends don't have constraints, they aren't constrained, and
     // thus don't fall under temp.friend p9. Else the simple presence of a
     // constraint makes them unique.
-    return getTrailingRequiresClause();
+    return !getTrailingRequiresClause().isNull();
   }
 
   return FriendConstraintRefersToEnclosingTemplate();
@@ -5453,7 +5453,7 @@ FunctionDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation StartLoc,
                      TypeSourceInfo *TInfo, StorageClass SC, bool UsesFPIntrin,
                      bool isInlineSpecified, bool hasWrittenPrototype,
                      ConstexprSpecKind ConstexprKind,
-                     Expr *TrailingRequiresClause) {
+                     const AssociatedConstraint &TrailingRequiresClause) {
   FunctionDecl *New = new (C, DC) FunctionDecl(
       Function, C, DC, StartLoc, NameInfo, T, TInfo, SC, UsesFPIntrin,
       isInlineSpecified, ConstexprKind, TrailingRequiresClause);
@@ -5464,7 +5464,8 @@ FunctionDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation StartLoc,
 FunctionDecl *FunctionDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID) {
   return new (C, ID) FunctionDecl(
       Function, C, nullptr, SourceLocation(), DeclarationNameInfo(), QualType(),
-      nullptr, SC_None, false, false, ConstexprSpecKind::Unspecified, nullptr);
+      nullptr, SC_None, false, false, ConstexprSpecKind::Unspecified,
+      /*TrailingRequiresClause=*/{});
 }
 
 BlockDecl *BlockDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L) {