Make some VM libraries patch cleanly using the analyzer.

sdk/lib/internal/symbol.dart

 // Copyright (c) 2013, 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.
 
 part of dart._internal;
 
 /**
  * Implementation of [core.Symbol].  This class uses the same name as
  * a core class so a user can't tell the difference.
  *
@@ skipping 96 matching lines @@
   const Symbol.unvalidated(this._name);
 
   // This is called by dart2js.
   Symbol.validated(String name)
       : this._name = validatePublicSymbol(name);
 
   bool operator ==(other) => other is Symbol && _name == other._name;
 
   external int get hashCode;
 
-  toString() => 'Symbol("$_name")';
+  external toString();

[hausner, 2016/12/14 23:35:40]

Why is it necessary to patch toString()? Isn't the implementation the same for
all platforms?

[Siggi Cherem (dart-lang), 2016/12/15 00:31:46]

It seems like the vm was patching it with some extra conversion to change names
like "set:foo' to 'foo=': 
https://github.com/dart-lang/sdk/blob/master/runtime/lib/symbol_patch.dart#L9

Is the VM patch is no longer necessary?


I also noticed that we are getting some inconsistent results among tools: this
program prints 'foo=' in the VM, and produces compile-time errors in dart2js and
analyzer:

main() {
  print(const Symbol('set:foo'));
}

[Lasse Reichstein Nielsen, 2016/12/15 07:55:41]

That's http://dartbug.com/13596 - the VM isn't validating arguments to the
Symbol constructor.

It's somewhat morally defensible since a const constructor can't really validate
anything, but it could be handled by special-casing.

 
   /// Platform-private accessor which cannot be called from user libraries.
   static String getName(Symbol symbol) => symbol._name;
 
   static String validatePublicSymbol(String name) {
     if (name.isEmpty || publicSymbolPattern.hasMatch(name)) return name;
     if (name.startsWith('_')) {
       // There may be other private parts in a qualified name than the first
       // one, but this is a common case that deserves a specific error
       // message.
       throw new ArgumentError('"$name" is a private identifier');
     }
     throw new ArgumentError(
         '"$name" is not a valid (qualified) symbol name');
   }
 
   /**
    * Checks whether name is a valid symbol name.
    *
    * This test allows both private and non-private symbols.
    */
   static bool isValidSymbol(String name) {
     return (name.isEmpty || symbolPattern.hasMatch(name));
   }
 }