Always build a builtin operator expression for the __extension__ unary operator.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@88811 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index b311fda..0d4ce60 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -5711,7 +5711,8 @@
                                             UnaryOperator::Opcode Opc,
                                             ExprArg input) {
   Expr *Input = (Expr*)input.get();
-  if (getLangOptions().CPlusPlus && Input->getType()->isOverloadableType()) {
+  if (getLangOptions().CPlusPlus && Input->getType()->isOverloadableType() &&
+      Opc != UnaryOperator::Extension) {
     // Find all of the overloaded operators visible from this
     // point. We perform both an operator-name lookup from the local
     // scope and an argument-dependent lookup based on the types of
diff --git a/test/SemaCXX/overloaded-builtin-operators.cpp b/test/SemaCXX/overloaded-builtin-operators.cpp
index 89ac29a..fd0cbc6 100644
--- a/test/SemaCXX/overloaded-builtin-operators.cpp
+++ b/test/SemaCXX/overloaded-builtin-operators.cpp
@@ -185,3 +185,6 @@
   return a[X][X];
 }
 
+void f() {
+  (void)__extension__(A());
+}