Make the RAII extension warning silencing for __extension__ a bit 
narrower, so it doesn't catch expresions that aren't sub-expressions of
__extension__ operator.

llvm-svn: 71967
diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 20c55a1..55fc0cd 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -225,8 +225,14 @@
 /// process of disambiguating between an expression and a declaration.
 Parser::OwningExprResult
 Parser::ParseExpressionWithLeadingExtension(SourceLocation ExtLoc) {
-  OwningExprResult LHS(ParseCastExpression(false));
-  if (LHS.isInvalid()) return move(LHS);
+  OwningExprResult LHS(Actions, true);
+  {
+    // Silence extension warnings in the sub-expression
+    ExtensionRAIIObject O(Diags);
+
+    LHS = ParseCastExpression(false);
+    if (LHS.isInvalid()) return move(LHS);
+  }
 
   LHS = Actions.ActOnUnaryOp(CurScope, ExtLoc, tok::kw___extension__,
                              move(LHS));