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

3 files changed, 20 insertions, 6 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()) {
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 91b9c6a5880..28f038a69e3 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -11460,14 +11460,15 @@ Decl *Sema::ActOnTemplatedFriendTag(Scope *S, SourceLocation FriendLoc,
       bool Owned = false;
       bool IsDependent = false;
       return ActOnTag(S, TagSpec, TUK_Friend, TagLoc, SS, Name, NameLoc,
-                      Attr, AS_public, 
+                      Attr, AS_public,
                       /*ModulePrivateLoc=*/SourceLocation(),
-                      MultiTemplateParamsArg(), Owned, IsDependent, 
+                      MultiTemplateParamsArg(), Owned, IsDependent,
                       /*ScopedEnumKWLoc=*/SourceLocation(),
                       /*ScopedEnumUsesClassTag=*/false,
-                      /*UnderlyingType=*/TypeResult());          
+                      /*UnderlyingType=*/TypeResult(),
+                      /*IsTypeSpecifier=*/false);
     }
-    
+
     NestedNameSpecifierLoc QualifierLoc = SS.getWithLocInContext(Context);
     ElaboratedTypeKeyword Keyword
       = TypeWithKeyword::getKeywordForTagTypeKind(Kind);
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 4f050345bc8..b468e31f097 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -7101,7 +7101,8 @@ Sema::ActOnExplicitInstantiation(Scope *S,
                         KWLoc, SS, Name, NameLoc, Attr, AS_none,
                         /*ModulePrivateLoc=*/SourceLocation(),
                         MultiTemplateParamsArg(), Owned, IsDependent,
-                        SourceLocation(), false, TypeResult());
+                        SourceLocation(), false, TypeResult(),
+                        /*IsTypeSpecifier*/false);
   assert(!IsDependent && "explicit instantiation of dependent name not yet handled");
 
   if (!TagD)