Introduce element categories and move resolver towards being more compositional.

dart/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 639 matching lines @@
       token = parseIdentifier(token.next);
     }
     token = parseFormalParameters(token);
     token = parseFunctionBody(token, false);
     listener.endFactoryMethod(factoryKeyword, period, token);
     return token.next;
   }
 
   Token parseOperatorName(Token token) {
     assert(optional('operator', token));
-    if (isUserDefinableOperator(token.next)) {
+    if (isUserDefinableOperator(token.next.stringValue)) {
       Token operator = token;
       token = token.next;
       listener.handleOperatorName(operator, token);
       return token.next;
     } else {
       return parseIdentifier(token);
     }
   }
 
-  bool isUserDefinableOperator(Token token) {
-    String value = token.stringValue;
-    return
-      (value === '==') ||
-      (value === '~') ||
-      (value === 'negate') ||
-      (value === '[]') ||
-      (value === '[]=') ||
-      (value === '*') ||
-      (value === '/') ||
-      (value === '%') ||
-      (value === '~/') ||
-      (value === '+') ||
-      (value === '-') ||
-      (value === '<<') ||
-      (value === '>>>') ||
-      (value === '>>') ||
-      (value === '>=') ||
-      (value === '>') ||
-      (value === '<=') ||
-      (value === '<') ||
-      (value === '&') ||
-      (value === '^') ||
-      (value === '|');
-  }
-
   Token parseFunction(Token token, Token getOrSet) {
     listener.beginFunction(token);
     token = parseModifiers(token);
     if (getOrSet === token) token = token.next;
     token = parseReturnTypeOpt(token);
     if (getOrSet === token) token = token.next;
     listener.beginFunctionName(token);
     if (optional('operator', token)) {
       token = parseOperatorName(token);
     } else {
@@ skipping 945 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }