Parse unary plus corretly (i.e., by ignoring it when it's valid).

frog/leg/scanner/parser.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * An event generating parser of Dart programs. This parser expects
  * all tokens in a linked list.
  */
 class Parser {
   final Listener listener;
@@ skipping 924 matching lines @@
         info = token.info;
         tokenLevel = info.precedence;
       }
     }
     return token;
   }
 
   Token parseUnaryExpression(Token token) {
     String value = token.stringValue;
     // Prefix:
-    if ((value === '!') ||
-        (value === '+') || // TODO(ahe): Being removed from specification.
-        (value === '-') ||
-        (value === '~')) {
+    if (value === '+') {
+      // Dart only allows "prefix plus" as an initial part of a
+      // decimal literal. We scan it as a separate token and then throw
+      // it away here when we know that we have a unary plus, not a

[ahe, 2012/02/03 13:19:11]

We are not throwing it away anymore :-)

+      // binary one.
+      Token operator = token;
+      Token next = token.next;
+      if (next.charOffset !== token.charOffset + 1 ||
+          (next.kind !== INT_TOKEN && next.kind !== DOUBLE_TOKEN)) {
+        listener.recoverableError("Unexpected token '+'", token: token);
+      }
+      token = parsePrecedenceExpression(next, POSTFIX_PRECEDENCE);
+      listener.handleUnaryPrefixExpression(operator);
+    } else if ((value === '!') ||
+               (value === '-') ||
+               (value === '~')) {
       Token operator = token;
       // Right associative, so we recurse at the same precedence
       // level.
       token = parsePrecedenceExpression(token.next, POSTFIX_PRECEDENCE);
       listener.handleUnaryPrefixExpression(operator);
     } else if ((value === '++') || value === '--') {
       // TODO(ahe): Validate this is used correctly.
       Token operator = token;
       // Right associative, so we recurse at the same precedence
       // level.
@@ skipping 645 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }