In LookupResult::resolveKind(), when handling multiple found declarations, ignore invalid declarations.

This reduces the "ambiguous reference" errors (which are rather strange in C/ObjC) and fixes an assertion hit
with an invalid code test case.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175869 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index a4228a5..d931bc7 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -371,6 +371,12 @@
     NamedDecl *D = Decls[I]->getUnderlyingDecl();
     D = cast<NamedDecl>(D->getCanonicalDecl());
 
+    // Ignore an invalid declaration unless it's the only one left.
+    if (D->isInvalidDecl() && I < N-1) {
+      Decls[I] = Decls[--N];
+      continue;
+    }
+
     // Redeclarations of types via typedef can occur both within a scope
     // and, through using declarations and directives, across scopes. There is
     // no ambiguity if they all refer to the same type, so unique based on the