When we parse a tag specifier, keep track of whether that tag

specifier resulted in the creation of a new TagDecl node, which
happens either when the tag specifier was a definition or when the tag
specifier was the first declaration of that tag type. This information
has several uses, the first of which is implemented in this commit:

  1) In C++, one is not allowed to define tag types within a type
  specifier (e.g., static_cast<struct S { int x; } *>(0) is
  ill-formed) or within the result or parameter types of a
  function. We now diagnose this.

  2) We can extend DeclGroups to contain information about any tags
  that are declared/defined within the declaration specifiers of a
  variable, e.g.,

    struct Point { int x, y, z; } p;

  This will help improve AST printing and template instantiation,
  among other things.

  3) For C99, we can keep track of whether a tag type is defined
  within the type of a parameter, to properly cope with cases like,
  e.g.,

    int bar(struct T2 { int x; } y) {
      struct T2 z;
    }

  We can also do similar things wherever there is a type specifier,
  e.g., to keep track of where the definition of S occurs in this
  legal C99 code:

    (struct S { int x, y; } *)0

  



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@72555 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 30 insertions, 4 deletions

diff --git a/lib/Sema/SemaType.cpp b/lib/Sema/SemaType.cpp
index 298a6cddda..83f9b60fd7 100644
--- a/lib/Sema/SemaType.cpp
+++ b/lib/Sema/SemaType.cpp
@@ -604,7 +604,12 @@ QualType Sema::BuildFunctionType(QualType T,
 /// GetTypeForDeclarator - Convert the type for the specified
 /// declarator to Type instances. Skip the outermost Skip type
 /// objects.
-QualType Sema::GetTypeForDeclarator(Declarator &D, Scope *S, unsigned Skip) {
+///
+/// If OwnedDecl is non-NULL, and this declarator's decl-specifier-seq
+/// owns the declaration of a type (e.g., the definition of a struct
+/// type), then *OwnedDecl will receive the owned declaration.
+QualType Sema::GetTypeForDeclarator(Declarator &D, Scope *S, unsigned Skip,
+                                    TagDecl **OwnedDecl) {
   bool OmittedReturnType = false;
 
   if (D.getContext() == Declarator::BlockLiteralContext
@@ -637,6 +642,8 @@ QualType Sema::GetTypeForDeclarator(Declarator &D, Scope *S, unsigned Skip) {
       T = ConvertDeclSpecToType(DS, D.getIdentifierLoc(), isInvalid);
       if (isInvalid)
         D.setInvalidType(true);
+      else if (OwnedDecl && DS.isTypeSpecOwned())
+        *OwnedDecl = cast<TagDecl>((Decl *)DS.getTypeRep());
     }
     break;
   }
@@ -717,6 +724,15 @@ QualType Sema::GetTypeForDeclarator(Declarator &D, Scope *S, unsigned Skip) {
         D.setInvalidType(true);
       }
 
+      if (getLangOptions().CPlusPlus && D.getDeclSpec().isTypeSpecOwned()) {
+        // C++ [dcl.fct]p6:
+        //   Types shall not be defined in return or parameter types.
+        TagDecl *Tag = cast<TagDecl>((Decl *)D.getDeclSpec().getTypeRep());
+        if (Tag->isDefinition())
+          Diag(Tag->getLocation(), diag::err_type_defined_in_result_type)
+            << Context.getTypeDeclType(Tag);
+      }
+
       if (FTI.NumArgs == 0) {
         if (getLangOptions().CPlusPlus) {
           // C++ 8.3.5p2: If the parameter-declaration-clause is empty, the
@@ -971,14 +987,24 @@ Sema::TypeResult Sema::ActOnTypeName(Scope *S, Declarator &D) {
   // the parser.
   assert(D.getIdentifier() == 0 && "Type name should have no identifier!");
   
-  QualType T = GetTypeForDeclarator(D, S);
+  TagDecl *OwnedTag = 0;
+  QualType T = GetTypeForDeclarator(D, S, /*Skip=*/0, &OwnedTag);
   if (D.isInvalidType())
     return true;
 
-  // Check that there are no default arguments (C++ only).
-  if (getLangOptions().CPlusPlus)
+  if (getLangOptions().CPlusPlus) {
+    // Check that there are no default arguments (C++ only).
     CheckExtraCXXDefaultArguments(D);
 
+    // C++0x [dcl.type]p3:
+    //   A type-specifier-seq shall not define a class or enumeration
+    //   unless it appears in the type-id of an alias-declaration
+    //   (7.1.3).
+    if (OwnedTag && OwnedTag->isDefinition())
+      Diag(OwnedTag->getLocation(), diag::err_type_defined_in_type_specifier)
+        << Context.getTypeDeclType(OwnedTag);
+  }
+
   return T.getAsOpaquePtr();
 }