First stab at parsing redirecting constructors.

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 823 matching lines @@
     }
     listener.endClassBody(count, begin, token);
     return token;
   }
 
   bool isGetOrSet(Token token) {
     final String value = token.stringValue;
     return (value === 'get') || (value === 'set');
   }
 
+  bool isFactoryDeclaration(Token token) {
+    if (optional('external', token)) token = token.next;
+    if (optional('const', token)) token = token.next;
+    return optional('factory', token);
+  }
+
   Token parseMember(Token token) {
     token = parseMetadataStar(token);
     String value = token.stringValue;
-    if (value === 'factory' ||
-        (value === 'external' && optional('factory', token.next))) {
+    if (isFactoryDeclaration(token)) {
       return parseFactoryMethod(token);
     }
     Token start = token;
     listener.beginMember(token);
 
     Link<Token> identifiers = findMemberName(token);
     if (identifiers.isEmpty()) {
       return listener.unexpected(start);
     }
     Token name = identifiers.head;
@@ skipping 79 matching lines @@
       token = parseQualifiedRestOpt(token);
       token = parseFormalParametersOpt(token);
       token = parseInitializersOpt(token);
       token = parseFunctionBody(token, false);
       listener.endMethod(getOrSet, start, token);
     }
     return token.next;
   }
 
   Token parseFactoryMethod(Token token) {
-    assert((optional('external', token) && optional('factory', token.next)) ||
-           optional('factory', token));
+    assert(isFactoryDeclaration(token));
     Token start = token;
     if (token.stringValue === 'external') token = token.next;
+    Token constKeyword = null;
+    if (optional('const', token)) {
+      constKeyword = token;
+      token = token.next;
+    }
     Token factoryKeyword = token;
     listener.beginFactoryMethod(factoryKeyword);
     token = token.next; // Skip 'factory'.
     token = parseIdentifier(token);
     token = parseQualifiedRestOpt(token);
     token = parseTypeVariablesOpt(token);
     Token period = null;
     if (optional('.', token)) {
       period = token;
       token = parseIdentifier(token.next);
     }
     token = parseFormalParameters(token);
-    token = parseFunctionBody(token, false);
+    if (optional('=', token)) {
+      token = parseRedirectingFactoryBody(token);
+    } else {
+      token = parseFunctionBody(token, false);
+    }
     listener.endFactoryMethod(start, period, token);
     return token.next;
   }
 
   Token parseOperatorName(Token token) {
     assert(optional('operator', token));
     if (isUserDefinableOperator(token.next.stringValue)) {
       Token operator = token;
       token = token.next;
       listener.handleOperatorName(operator, token);
@@ skipping 54 matching lines @@
     token = parseIdentifier(token);
     listener.endFunctionName(token);
     token = parseFormalParameters(token);
     listener.handleNoInitializers();
     bool isBlock = optional('{', token);
     token = parseFunctionBody(token, true);
     listener.endFunction(null, token);
     return isBlock ? token.next : token;
   }
 
+  Token parseQualifiedList(Token token) {
+    listener.beginQualifiedList(token);
+    Token parseQualifiedPart(Token token) {

[ahe, 2012/10/09 10:51:37]

Why is this a nested function?

[Lasse Reichstein Nielsen, 2012/10/09 11:51:26]

because I didn't want to duplicate the code, but it has no obvious use outside
this function.
If I had a better loop construct, I wouldn't need it.

[ahe, 2012/10/09 12:16:51]

There is no reason to create extra overhead by creating a closure each time.
Please don't do it in the parser.

Also, there is always a use for the function outside this method. It is not like
we have tried keeping the number of parseFoo methods small.

+      Token start = token;
+      token = parseIdentifier(token);
+      token = parseTypeVariablesOpt(token);
+      listener.endType(start, null);
+      return token;
+    }
+    Token beginToken = token;
+    token = parseQualifiedPart(token);
+    int count = 1;
+    while (optional('.', token)) {
+      token = parseQualifiedPart(token.next);
+      count++;
+    }
+    listener.endQualifiedList(count);
+    return token;
+  }
+
+  Token parseRedirectingFactoryBody(Token token) {
+    assert(optional('=', token));
+    Token equals = token;
+    listener.beginRedirectingFactoryBody(token);

[ahe, 2012/10/09 10:51:37]

Move this before the assert.

[Lasse Reichstein Nielsen, 2012/10/09 11:51:26]

Done.

+    token = parseQualifiedList(token.next);
+    Token semicolon = token;
+    expectSemicolon(token);
+    listener.endRedirectingFactoryBody(equals, semicolon);
+    return token;
+  }
+
   Token parseFunctionBody(Token token, bool isExpression) {
     if (optional(';', token)) {
       listener.endFunctionBody(0, null, token);
       return token;
     } else if (optional('=>', token)) {
       Token begin = token;
       token = parseExpression(token.next);
       if (!isExpression) {
         expectSemicolon(token);
         listener.endReturnStatement(true, begin, token);
@@ skipping 1041 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }