Attaching comments to declarations: don't attach comments to implicit declarations.

llvm-svn: 159354
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 9fb2dc1..820288e 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -61,6 +61,10 @@
 
   assert(D);
 
+  // User can not attach documentation to implicit declarations.
+  if (D->isImplicit())
+    return NULL;
+
   // TODO: handle comments for function parameters properly.
   if (isa<ParmVarDecl>(D))
     return NULL;