Implement substitution for type variables.

sdk/lib/_internal/compiler/implementation/js_backend/namer.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.
 
 part of js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class Namer implements ClosureNamer {
@@ skipping 505 matching lines @@
     String newName = getMappedGlobalName('${getName(element)}\$bailout');
     return '$CURRENT_ISOLATE.$newName';
   }
 
   String isolateLazyInitializerAccess(Element element) {
     return "$CURRENT_ISOLATE.${getLazyInitializerName(element)}";
   }
 
   String operatorIsPrefix() => r'$is';
 
+  String operatorAsPrefix() => r'$as';
+
   String operatorIs(Element element) {
     // TODO(erikcorry): Reduce from $isx to ix when we are minifying.
     return '${operatorIsPrefix()}${getName(element)}';
   }
 
   /*
    * Returns a name that does not clash with reserved JS keywords,
    * and also ensures it won't clash with other identifiers.
    */
   String safeName(String name) {
     if (jsReserved.contains(name) || name.startsWith(r'$')) {
       name = '\$$name';
     }
     assert(!jsReserved.contains(name));
     return name;
   }
 
+  String substitutionName(Element element) {
+    return '${operatorAsPrefix()}${getName(element)}';
+  }
+
   String oneShotInterceptorName(Selector selector) {
     // TODO(ngeoffray): What to do about typed selectors? We could
     // filter them out, or keep them and hope the generated one shot
     // interceptor takes advantage of the type.
     String cached = oneShotInterceptorNames[selector];
     if (cached != null) return cached;
     SourceString name = operatorNameToIdentifier(selector.name);
     String result = getFreshName(name.slowToString(), usedGlobalNames);
     oneShotInterceptorNames[selector] = result;
     return result;
@@ skipping 42 matching lines @@
       return const SourceString(r'$or');
     } else if (value == '-') {
       return const SourceString(r'$sub');
     } else if (value == 'unary-') {
       return const SourceString(r'$negate');
     } else {
       return name;
     }
   }
 }