Generate a resolution error if a unary + is used for something other than numbers.

frog/leg/tree/nodes.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.
 
 interface Visitor<R> {
   R visitBlock(Block node);
   R visitBreakStatement(BreakStatement node);
   R visitCatchBlock(CatchBlock node);
   R visitClassNode(ClassNode node);
   R visitConditional(Conditional node);
@@ skipping 223 matching lines @@
   }
   bool get isOperator() => selector is Operator;
   bool get isPropertyAccess() => argumentsNode === null;
   bool get isFunctionObjectInvocation() => selector === null;
   bool get isPrefix() => argumentsNode is Prefix;
   bool get isPostfix() => argumentsNode is Postfix;
   bool get isIndex() =>
       isOperator && selector.asOperator().source.stringValue === '[]';
 
   Token getBeginToken() {
+    if (isPrefix && !isIndex) return selector.getBeginToken();
     return firstBeginToken(receiver, selector);
   }
 
   Token getEndToken() {
-    Token token;
-    if (argumentsNode !== null) token = argumentsNode.getEndToken();
-    if (token !== null) return token;
-    if (selector !== null) {
-      return selector.getEndToken();
-    }
+    if (isPrefix) return firstBeginToken(receiver, selector);
+    if (argumentsNode !== null) return argumentsNode.getEndToken();
+    if (selector !== null) return selector.getEndToken();
     return receiver.getBeginToken();
   }
 
   Send copyWithReceiver(Node receiver) {
     return new Send(receiver, selector, argumentsNode);
   }
 }
 
 class Postfix extends NodeList {
   // TODO(floitsch): pass const EmptyLink<Node>() to super.
@@ skipping 1179 matching lines @@
 
   visitChildren(Visitor visitor) {
     formals.accept(visitor);
     block.accept(visitor);
   }
 
   Token getBeginToken() => catchKeyword;
 
   Token getEndToken() => block.getEndToken();
 }