More fixes for places where 'decltype(auto)' is permitted in the C++ grammar but makes no sense.

llvm-svn: 294509

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -1944,6 +1944,8 @@ def err_auto_bitfield : Error<
   "cannot pass bit-field as __auto_type initializer in C">;
 
 // C++1y decltype(auto) type
+def err_decltype_auto_invalid : Error<
+  "'decltype(auto)' not allowed here">;
 def err_decltype_auto_cannot_be_combined : Error<
   "'decltype(auto)' cannot be combined with other type specifiers">;
 def err_decltype_auto_function_declarator_not_declaration : Error<

clang/include/clang/Sema/Sema.h

@@ -4749,7 +4749,8 @@ public:
                                ParsedType ObjectType,
                                bool EnteringContext);
 
-  ParsedType getDestructorType(const DeclSpec& DS, ParsedType ObjectType);
+  ParsedType getDestructorTypeForDecltype(const DeclSpec &DS,
+                                          ParsedType ObjectType);
 
   // Checks that reinterpret casts don't have undefined behavior.
   void CheckCompatibleReinterpretCast(QualType SrcType, QualType DestType,

clang/lib/Parse/ParseExprCXX.cpp

@@ -2580,7 +2580,8 @@ bool Parser::ParseUnqualifiedId(CXXScopeSpec &SS, bool EnteringContext,
     if (SS.isEmpty() && Tok.is(tok::kw_decltype)) {
       DeclSpec DS(AttrFactory);
       SourceLocation EndLoc = ParseDecltypeSpecifier(DS);
-      if (ParsedType Type = Actions.getDestructorType(DS, ObjectType)) {
+      if (ParsedType Type =
+              Actions.getDestructorTypeForDecltype(DS, ObjectType)) {
         Result.setDestructorName(TildeLoc, Type, EndLoc);
         return false;
       }

clang/lib/Sema/SemaDeclCXX.cpp

@@ -3728,6 +3728,9 @@ Sema::BuildMemInitializer(Decl *ConstructorD,
     BaseType = GetTypeFromParser(TemplateTypeTy, &TInfo);
   } else if (DS.getTypeSpecType() == TST_decltype) {
     BaseType = BuildDecltypeType(DS.getRepAsExpr(), DS.getTypeSpecTypeLoc());
+  } else if (DS.getTypeSpecType() == TST_decltype_auto) {
+    Diag(DS.getTypeSpecTypeLoc(), diag::err_decltype_auto_invalid);
+    return true;
   } else {
     LookupResult R(*this, MemberOrBase, IdLoc, LookupOrdinaryName);
     LookupParsedName(R, S, &SS);

clang/lib/Sema/SemaExprCXX.cpp

@@ -323,20 +323,31 @@ ParsedType Sema::getDestructorName(SourceLocation TildeLoc,
   return nullptr;
 }
 
-ParsedType Sema::getDestructorType(const DeclSpec& DS, ParsedType ObjectType) {
-    if (DS.getTypeSpecType() == DeclSpec::TST_error || !ObjectType)
-      return nullptr;
-    assert(DS.getTypeSpecType() == DeclSpec::TST_decltype
-           && "only get destructor types from declspecs");
-    QualType T = BuildDecltypeType(DS.getRepAsExpr(), DS.getTypeSpecTypeLoc());
-    QualType SearchType = GetTypeFromParser(ObjectType);
-    if (SearchType->isDependentType() || Context.hasSameUnqualifiedType(SearchType, T)) {
-      return ParsedType::make(T);
-    }
+ParsedType Sema::getDestructorTypeForDecltype(const DeclSpec &DS,
+                                              ParsedType ObjectType) {
+  if (DS.getTypeSpecType() == DeclSpec::TST_error)
+    return nullptr;
 
+  if (DS.getTypeSpecType() == DeclSpec::TST_decltype_auto) {
+    Diag(DS.getTypeSpecTypeLoc(), diag::err_decltype_auto_invalid);
+    return nullptr;
+  }
+
+  assert(DS.getTypeSpecType() == DeclSpec::TST_decltype &&
+         "unexpected type in getDestructorType");
+  QualType T = BuildDecltypeType(DS.getRepAsExpr(), DS.getTypeSpecTypeLoc());
+
+  // If we know the type of the object, check that the correct destructor
+  // type was named now; we can give better diagnostics this way.
+  QualType SearchType = GetTypeFromParser(ObjectType);
+  if (!SearchType.isNull() && !SearchType->isDependentType() &&
+      !Context.hasSameUnqualifiedType(T, SearchType)) {
     Diag(DS.getTypeSpecTypeLoc(), diag::err_destructor_expr_type_mismatch)
       << T << SearchType;
     return nullptr;
+  }
+
+  return ParsedType::make(T);
 }
 
 bool Sema::checkLiteralOperatorId(const CXXScopeSpec &SS,

clang/test/SemaCXX/cxx1y-deduced-return-type.cpp

@@ -385,16 +385,31 @@ namespace MemberTemplatesWithDeduction {
 }
 }
 
-namespace NNS {
-  int n;
-  decltype(auto) i();
-  decltype(n) j();
-  struct X {
-    // We resolve a wording bug here: 'decltype(auto)::' should not be parsed
-    // as a nested-name-specifier.
-    friend decltype(auto) ::NNS::i();
-    friend decltype(n) ::NNS::j(); // expected-error {{not a class}}
-  };
+// We resolve a wording bug here: 'decltype(auto)' should not be modeled as a
+// decltype-specifier, just as a simple-type-specifier. All the extra places
+// where a decltype-specifier can appear make no sense for 'decltype(auto)'.
+namespace DecltypeAutoShouldNotBeADecltypeSpecifier {
+  namespace NNS {
+    int n;
+    decltype(auto) i();
+    decltype(n) j();
+    struct X {
+      friend decltype(auto) ::DecltypeAutoShouldNotBeADecltypeSpecifier::NNS::i();
+      friend decltype(n) ::DecltypeAutoShouldNotBeADecltypeSpecifier::NNS::j(); // expected-error {{not a class}}
+    };
+  }
+
+  namespace Dtor {
+    struct A {};
+    void f(A a) { a.~decltype(auto)(); } // expected-error {{'decltype(auto)' not allowed here}}
+  }
+
+  namespace BaseClass {
+    struct A : decltype(auto) {}; // expected-error {{'decltype(auto)' not allowed here}}
+    struct B {
+      B() : decltype(auto)() {} // expected-error {{'decltype(auto)' not allowed here}}
+    };
+  }
 }
 
 namespace CurrentInstantiation {