Parse argument definition test expressions.

dart/lib/compiler/implementation/scanner/parser.dart

 // Copyright (c) 2012, 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 (aka a token stream).
  *
  * The class [Scanner] is used to generate a token stream. See the
  * file scanner.dart.
@@ skipping 1188 matching lines @@
       } else {
         return listener.expectedExpression(token);
       }
     } else if (kind === OPEN_PAREN_TOKEN) {
       return parseParenthesizedExpressionOrFunctionLiteral(token);
     } else if ((kind === LT_TOKEN) ||
                (kind === OPEN_SQUARE_BRACKET_TOKEN) ||
                (kind === OPEN_CURLY_BRACKET_TOKEN) ||
                token.stringValue === '[]') {
       return parseLiteralListOrMap(token);
+    } else if (kind === QUESTION_TOKEN) {
+      return parseArgumentDefinitionTest(token);
     } else {
       return listener.expectedExpression(token);
     }
   }
 
+  Token parseArgumentDefinitionTest(Token token) {
+    Token questionToken = token;
+    listener.beginArgumentDefinitionTest(questionToken);
+    assert(optional('?', token));
+    token = parseIdentifier(token.next);
+    listener.endArgumentDefinitionTest(questionToken, token);
+    return token;
+  }
+
   Token parseParenthesizedExpressionOrFunctionLiteral(Token token) {
     BeginGroupToken beginGroup = token;
     int kind = beginGroup.endGroup.next.kind;
     if (mayParseFunctionExpressions &&
         (kind === FUNCTION_TOKEN || kind === OPEN_CURLY_BRACKET_TOKEN)) {
       return parseUnamedFunction(token);
     } else {
       bool old = mayParseFunctionExpressions;
       mayParseFunctionExpressions = true;
       token = parseParenthesizedExpression(token);
@@ skipping 616 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }