PR18234: Mark a tag definition as invalid early if it appears in a

type-specifier in C++. Some checks will assert in this case otherwise (in
particular, the access specifier may be missing if this happens inside a class
definition, due to a violation of an AST invariant).

llvm-svn: 198721

1 files changed, 13 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 07a551da2f1..7cdf81a87e4 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -10396,6 +10396,9 @@ bool Sema::isAcceptableTagRedeclaration(const TagDecl *Previous,
 /// former case, Name will be non-null.  In the later case, Name will be null.
 /// TagSpec indicates what kind of tag this is. TUK indicates whether this is a
 /// reference/declaration/definition of a tag.
+///
+/// IsTypeSpecifier is true if this is a type-specifier (or
+/// trailing-type-specifier) other than one in an alias-declaration.
 Decl *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
                      SourceLocation KWLoc, CXXScopeSpec &SS,
                      IdentifierInfo *Name, SourceLocation NameLoc,
@@ -10405,7 +10408,8 @@ Decl *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
                      bool &OwnedDecl, bool &IsDependent,
                      SourceLocation ScopedEnumKWLoc,
                      bool ScopedEnumUsesClassTag,
-                     TypeResult UnderlyingType) {
+                     TypeResult UnderlyingType,
+                     bool IsTypeSpecifier) {
   // If this is not a definition, it must have a name.
   IdentifierInfo *OrigName = Name;
   assert((Name != 0 || TUK == TUK_Definition) &&
@@ -11016,6 +11020,14 @@ CreateNewDecl:
                                cast_or_null<RecordDecl>(PrevDecl));
   }
 
+  // C++11 [dcl.type]p3:
+  //   A type-specifier-seq shall not define a class or enumeration [...].
+  if (getLangOpts().CPlusPlus && IsTypeSpecifier && TUK == TUK_Definition) {
+    Diag(New->getLocation(), diag::err_type_defined_in_type_specifier)
+      << Context.getTagDeclType(New);
+    Invalid = true;
+  }
+
   // Maybe add qualifier info.
   if (SS.isNotEmpty()) {
     if (SS.isSet()) {