When we see the a '[' in a postfix expression in Objective-C, perform

a simple, quick check to determine whether the expression starting
with '[' can only be an Objective-C message send. If so, don't parse
it as an array subscript expression. This improves recovery for, e.g.,

  [a method1]
  [a method2]

so that we now produce

  t.m:10:13: error: expected ';' after expression
  [a method]
            ^

instead of some mess about expecting ']'.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@105221 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 18 insertions, 0 deletions

diff --git a/lib/Parse/ParseExpr.cpp b/lib/Parse/ParseExpr.cpp
index 8fb71c3ff6..093f9738ca 100644
--- a/lib/Parse/ParseExpr.cpp
+++ b/lib/Parse/ParseExpr.cpp
@@ -961,6 +961,9 @@ Parser::ParsePostfixExpressionSuffix(OwningExprResult LHS) {
     default:  // Not a postfix-expression suffix.
       return move(LHS);
     case tok::l_square: {  // postfix-expression: p-e '[' expression ']'
+      if (getLang().ObjC1 && isSimpleObjCMessageExpression())
+        return move(LHS);
+          
       Loc = ConsumeBracket();
       OwningExprResult Idx(ParseExpression());
 
diff --git a/lib/Parse/ParseObjc.cpp b/lib/Parse/ParseObjc.cpp
index b76b677af0..34b8187be5 100644
--- a/lib/Parse/ParseObjc.cpp
+++ b/lib/Parse/ParseObjc.cpp
@@ -1794,6 +1794,21 @@ bool Parser::ParseObjCXXMessageReceiver(bool &IsExpr, void *&TypeOrExpr) {
   return false;
 }
 
+/// \brief Determine whether the parser is currently referring to a an
+/// Objective-C message send, using a simplified heuristic to avoid overhead.
+///
+/// This routine will only return true for a subset of valid message-send
+/// expressions.
+bool Parser::isSimpleObjCMessageExpression() {
+  assert(Tok.is(tok::l_square) && 
+         "Incorrect start for isSimpleObjCMessageExpression");
+  if (!getLang().ObjC1)
+    return false;
+  
+  return GetLookAheadToken(1).is(tok::identifier) &&
+         GetLookAheadToken(2).is(tok::identifier);
+}
+
 ///   objc-message-expr:
 ///     '[' objc-receiver objc-message-args ']'
 ///