[Concepts] Function trailing requires clauses

Function trailing requires clauses now parsed, supported in overload resolution and when calling, referencing and taking the address of functions or function templates.

Differential Revision: https://reviews.llvm.org/D43357

1 files changed, 30 insertions, 9 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 92b115c8a3f..468db9cfc7f 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7895,7 +7895,13 @@ struct FindOverriddenMethod {
          Path.Decls = Path.Decls.slice(1)) {
       NamedDecl *D = Path.Decls.front();
       if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
-        if (MD->isVirtual() && !S->IsOverload(Method, MD, false))
+        if (MD->isVirtual() &&
+            !S->IsOverload(
+                Method, MD, /*UseMemberUsingDeclRules=*/false,
+                /*ConsiderCudaAttrs=*/true,
+                // C++2a [class.virtual]p2 does not consider requires clauses
+                // when overriding.
+                /*ConsiderRequiresClauses=*/false))
           return true;
       }
     }
@@ -8240,7 +8246,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
 
     NewFD = FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(), NameInfo,
                                  R, TInfo, SC, isInline, HasPrototype,
-                                 CSK_unspecified);
+                                 CSK_unspecified,
+                                 /*TrailingRequiresClause=*/nullptr);
     if (D.isInvalidType())
       NewFD->setInvalidDecl();
 
@@ -8257,6 +8264,7 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     ConstexprKind = CSK_unspecified;
     D.getMutableDeclSpec().ClearConstexprSpec();
   }
+  Expr *TrailingRequiresClause = D.getTrailingRequiresClause();
 
   // Check that the return type is not an abstract class type.
   // For record types, this is done by the AbstractClassUsageDiagnoser once
@@ -8276,7 +8284,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     return CXXConstructorDecl::Create(
         SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
         TInfo, ExplicitSpecifier, isInline,
-        /*isImplicitlyDeclared=*/false, ConstexprKind);
+        /*isImplicitlyDeclared=*/false, ConstexprKind, InheritedConstructor(),
+        TrailingRequiresClause);
 
   } else if (Name.getNameKind() == DeclarationName::CXXDestructorName) {
     // This is a C++ destructor declaration.
@@ -8285,8 +8294,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
       CXXRecordDecl *Record = cast<CXXRecordDecl>(DC);
       CXXDestructorDecl *NewDD = CXXDestructorDecl::Create(
           SemaRef.Context, Record, D.getBeginLoc(), NameInfo, R, TInfo,
-          isInline,
-          /*isImplicitlyDeclared=*/false, ConstexprKind);
+          isInline, /*isImplicitlyDeclared=*/false, ConstexprKind,
+          TrailingRequiresClause);
 
       // If the destructor needs an implicit exception specification, set it
       // now. FIXME: It'd be nice to be able to create the right type to start
@@ -8306,7 +8315,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
       return FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(),
                                   D.getIdentifierLoc(), Name, R, TInfo, SC,
                                   isInline,
-                                  /*hasPrototype=*/true, ConstexprKind);
+                                  /*hasPrototype=*/true, ConstexprKind,
+                                  TrailingRequiresClause);
     }
 
   } else if (Name.getNameKind() == DeclarationName::CXXConversionFunctionName) {
@@ -8323,9 +8333,14 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     IsVirtualOkay = true;
     return CXXConversionDecl::Create(
         SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
-        TInfo, isInline, ExplicitSpecifier, ConstexprKind, SourceLocation());
+        TInfo, isInline, ExplicitSpecifier, ConstexprKind, SourceLocation(),
+        TrailingRequiresClause);
 
   } else if (Name.getNameKind() == DeclarationName::CXXDeductionGuideName) {
+    if (TrailingRequiresClause)
+      SemaRef.Diag(TrailingRequiresClause->getBeginLoc(),
+                   diag::err_trailing_requires_clause_on_deduction_guide)
+          << TrailingRequiresClause->getSourceRange();
     SemaRef.CheckDeductionGuideDeclarator(D, R, SC);
 
     return CXXDeductionGuideDecl::Create(SemaRef.Context, DC, D.getBeginLoc(),
@@ -8347,7 +8362,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     // This is a C++ method declaration.
     CXXMethodDecl *Ret = CXXMethodDecl::Create(
         SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
-        TInfo, SC, isInline, ConstexprKind, SourceLocation());
+        TInfo, SC, isInline, ConstexprKind, SourceLocation(),
+        TrailingRequiresClause);
     IsVirtualOkay = !Ret->isStatic();
     return Ret;
   } else {
@@ -8361,7 +8377,7 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     //   - we're in C++ (where every function has a prototype),
     return FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(), NameInfo,
                                 R, TInfo, SC, isInline, true /*HasPrototype*/,
-                                ConstexprKind);
+                                ConstexprKind, TrailingRequiresClause);
   }
 }
 
@@ -10572,6 +10588,11 @@ bool Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
           }
         }
       }
+      if (Method->isVirtual() && NewFD->getTrailingRequiresClause())
+        // C++2a [class.virtual]p6
+        // A virtual method shall not have a requires-clause.
+        Diag(NewFD->getTrailingRequiresClause()->getBeginLoc(),
+             diag::err_constrained_virtual_method);
 
       if (Method->isStatic())
         checkThisInStaticMemberFunctionType(Method);