Fix for bug 1229: Unary operator plus is not allowed ... except for literals.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 3699)
+++ runtime/vm/parser.cc	(working copy)
@@ -5357,8 +5357,10 @@
 
 
 bool Parser::IsPrefixOperator(Token::Kind token) {
-  return token == Token::kADD || token == Token::kSUB
-      || token == Token::kNOT || token == Token::kBIT_NOT;
+  return (token == Token::kTIGHTADD) ||   // Valid for literals only!
+         (token == Token::kSUB) ||
+         (token == Token::kNOT) ||
+         (token == Token::kBIT_NOT);
 }
 
 
@@ -5384,6 +5386,9 @@
   while (current_preced >= min_preced) {
     while (Token::Precedence(CurrentToken()) == current_preced) {
       Token::Kind op_kind = CurrentToken();
+      if (op_kind == Token::kTIGHTADD) {
+        op_kind = Token::kADD;
+      }
       const intptr_t op_pos = token_index_;
       ConsumeToken();
       AstNode* right_operand = NULL;
@@ -5683,7 +5688,14 @@
     Token::Kind unary_op = CurrentToken();
     ConsumeToken();
     expr = ParseUnaryExpr();
-    expr = UnaryOpNode::UnaryOpOrLiteral(op_pos, unary_op, expr);
+    if (unary_op == Token::kTIGHTADD) {
+      if (!expr->IsLiteralNode()) {

[hausner, 2012/01/31 18:09:46]

This test is not strict enough. This also allows +"foo". You have to check for
number literals.

[srdjan, 2012/01/31 19:26:37]

Changed scanner to produce TIGHTADD only if the + is followed by a number
literal start. I.e., no extra test needed here (added comment here).

+        ErrorMsg("'+' is not a valid prefix");

[hausner, 2012/01/31 18:09:46]

I wouldn't call + a prefix. How about "unexpected operator '+'" ? Also, please
print the error message at the token location of the +.

[srdjan, 2012/01/31 19:26:37]

Using "unexpected". The other option would have been "is not a valid prefix
operator".

+      }
+      // Expression is the literal itself.
+    } else {
+      expr = UnaryOpNode::UnaryOpOrLiteral(op_pos, unary_op, expr);
+    }
   } else if (IsIncrementOperator(CurrentToken())) {
     Token::Kind incr_op = CurrentToken();
     ConsumeToken();