Fix names with '$' to not conflict with operators or internal helpers

frog/world.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.
 
 /** The one true [World]. */
 World world;
 
 /**
  * Experimental phase to enable await, only set when using the
  * await/awaitc.dart entrypoint.
@@ skipping 211 matching lines @@
     var ret = new DefinedType(name, corelib, null, isClass);
     corelib.types[name] = ret;
     return ret;
   }
 
   // TODO(jimhug): Can this just be a const Set?
   Set<String> _jsKeywords;
 
   /** Ensures that identifiers are legal in the generated JS. */
   String toJsIdentifier(String name) {
+    if (name == null) return null;
     if (_jsKeywords == null) {
       // TODO(jmesserly): this doesn't work if I write "new Set<String>.from"
       // List of JS reserved words.
       _jsKeywords = new Set.from([
         'break', 'case', 'catch', 'continue', 'debugger', 'default',
         'delete', 'do', 'else', 'finally', 'for', 'function', 'if',
         'in', 'instanceof', 'new', 'return', 'switch', 'this', 'throw',
         'try', 'typeof', 'var', 'void', 'while', 'with',
         'class', 'enum', 'export', 'extends', 'import', 'super',
         'implements', 'interface', 'let', 'package', 'private',
         'protected', 'public', 'static', 'yield',
         'native']);
     }
     if (_jsKeywords.contains(name)) {
       return name + '_';
     } else {
-      // regexs here?  Is it worth checking all names - or just libraries?
-      return name;
+      // regexs for better perf?
+      return name.replaceAll(@'$', @'$$').replaceAll(':', @'$');
     }
   }
 
   bool compile() {
     // TODO(jimhug): Must have called setOptions - better errors.
     if (options.dartScript == null) {
       fatal('no script provided to compile');
       return false;
     }
 
@@ skipping 190 matching lines @@
 
   withTiming(String name, f()) {
     final sw = new Stopwatch();
     sw.start();
     var result = f();
     sw.stop();
     info('$name in ${sw.elapsedInMs()}msec');
     return result;
   }
 }