Provide the correct mangling and linkage for certain unnamed nested classes.

This corrects the mangling and linkage of classes (& their member functions) in
cases like this:

  struct foo {
    struct {
      void func() { ... }
    } x;
  };

we were accidentally giving this nested unnamed struct 'no' linkage where it
should've had the linkage of the outer class. The mangling was incorrecty too,
mangling as TU-wide unnamed type mangling of $_X rather than class-scoped
mangling of UtX_.

This also fixes -Wunused-member-function which would incorrectly diagnose
'func' as unused due to it having no linkage & thus appearing to be TU-local
when in fact it might be correctly used in another TU.

Similar mangling should be applied to function local classes in similar cases
but I've deferred that for a subsequent patch.

Review/discussion by Richard Smith, John McCall, & especially Eli Friedman.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167906 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 4 deletions

diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 74abbaa492..9569841a56 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -480,8 +480,7 @@ static LinkageInfo getLVForClassMember(const NamedDecl *D, bool OnlyTemplate) {
   if (!(isa<CXXMethodDecl>(D) ||
         isa<VarDecl>(D) ||
         isa<FieldDecl>(D) ||
-        (isa<TagDecl>(D) &&
-         (D->getDeclName() || cast<TagDecl>(D)->getTypedefNameForAnonDecl()))))
+        isa<TagDecl>(D)))
     return LinkageInfo::none();
 
   LinkageInfo LV;
@@ -2561,8 +2560,7 @@ void TagDecl::setTypedefNameForAnonDecl(TypedefNameDecl *TDD) {
 void TagDecl::startDefinition() {
   IsBeingDefined = true;
 
-  if (isa<CXXRecordDecl>(this)) {
-    CXXRecordDecl *D = cast<CXXRecordDecl>(this);
+  if (CXXRecordDecl *D = dyn_cast<CXXRecordDecl>(this)) {
     struct CXXRecordDecl::DefinitionData *Data = 
       new (getASTContext()) struct CXXRecordDecl::DefinitionData(D);
     for (redecl_iterator I = redecls_begin(), E = redecls_end(); I != E; ++I)