dart2js cps: Generate fast checks for 'is String' and 'is bool'.

pkg/compiler/lib/src/js_backend/codegen/codegen.dart

 // Copyright (c) 2014, 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.
 
 library code_generator;
 
 import 'glue.dart';
 
 import '../../closure.dart' show ClosureClassElement;
 import '../../common/codegen.dart' show CodegenRegistry;
@@ skipping 340 matching lines @@
   js.Expression visitTypeOperator(tree_ir.TypeOperator node) {
     js.Expression value = visitExpression(node.value);
     List<js.Expression> typeArguments = visitExpressionList(node.typeArguments);
     DartType type = node.type;
     if (type is InterfaceType) {
       glue.registerIsCheck(type, registry);
       ClassElement clazz = type.element;
 
       // Handle some special checks against classes that exist only in
       // the compile-time class hierarchy, not at runtime.
+      // TODO(sra): Is this correct? The field tests are only valid with the
+      // precondtion that [value] is an Array. They will crash on `null`.

[Siggi Cherem (dart-lang), 2015/08/21 23:57:11]

precondtion => precondition

[sra1, 2015/08/22 00:11:56]

Done.

       if (clazz == glue.jsExtendableArrayClass) {
+        assert(node.isTypeTest);
         return js.js(r'!#.fixed$length', <js.Expression>[value]);
       } else if (clazz == glue.jsMutableArrayClass) {
+        assert(node.isTypeTest);
         return js.js(r'!#.immutable$list', <js.Expression>[value]);
       }
 
+      if (glue.isStringClass(clazz)) {
+        if (node.isTypeTest) {
+          return js.js(r'typeof # === "string"', <js.Expression>[value]);
+        }
+        // TODO(sra): Implement fast cast via calling 'stringTypeCast'.
+      } else if (glue.isBoolClass(clazz)) {
+        if (node.isTypeTest) {
+          return js.js(r'typeof # === "boolean"', <js.Expression>[value]);
+        }
+        // TODO(sra): Implement fast cast via calling 'boolTypeCast'.
+      }
+
       // The helper we use needs the JSArray class to exist, but for some
       // reason the helper does not cause this dependency to be registered.
       // TODO(asgerf): Most programs need List anyway, but we should fix this.
       registry.registerInstantiatedClass(glue.listClass);
 
       // We use one of the two helpers:
       //
       //     checkSubtype(value, $isT, typeArgs, $asT)
       //     subtypeCast(value, $isT, typeArgs, $asT)
       //
@@ skipping 515 matching lines @@
   js.Expression visitAwait(tree_ir.Await node) {
     return new js.Await(visitExpression(node.input));
   }
 
   visitFunctionExpression(tree_ir.FunctionExpression node) {
     // FunctionExpressions are currently unused.
     // We might need them if we want to emit raw JS nested functions.
     throw 'FunctionExpressions should not be used';
   }
 }