Fix to PR16225 (Assert-on-invalid: isa<LabelDecl>(D) && "declaration not instantiated in this scope")

Differential Revision: http://llvm-reviews.chandlerc.com/D920

llvm-svn: 188137
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index ce7684c..315a405 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4063,6 +4063,9 @@
         isa<TemplateTemplateParmDecl>(D))
       return D;
 
+    if (D->isInvalidDecl())
+      return 0;
+
     // If we didn't find the decl, then we must have a label decl that hasn't
     // been found yet.  Lazily instantiate it and return it now.
     assert(isa<LabelDecl>(D));