partially implement instance of checks and some codegen fixes

lib/src/codegen/js_codegen.dart

 // Copyright (c) 2015, 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 dev_compiler.src.codegen.js_codegen;
 
 import 'dart:collection' show HashSet, HashMap;
 import 'dart:io' show Directory, File;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
@@ skipping 127 matching lines @@
         defaultValue
       ])
     ]);
   }
 
   JS.Statement _initPrivateSymbol(String name) => js.statement(
       'let # = $_SYMBOL(#);', [new JSTemporary(name), js.string(name, "'")]);
 
   // TODO(jmesserly): this is a temporary workaround for `Symbol` in core,
   // until we have better name tracking.
-  String get _SYMBOL => currentLibrary.isDartCore ? 'dart.JsSymbol' : 'Symbol';
+  String get _SYMBOL {
+    var name = currentLibrary.name;
+    if (name == 'dart.core' || name == 'dart._internal') return 'dart.JsSymbol';
+    return 'Symbol';
+  }
 
   @override
   JS.Statement visitCompilationUnit(CompilationUnit node) {
     var source = node.element.source;
 
     _constEvaluator = new ConstantEvaluator(source, rules.provider);
     _checkerReporter.enterSource(source);
 
     // TODO(jmesserly): scriptTag, directives.
     var body = <JS.Statement>[];
@@ skipping 1188 matching lines @@
     _properties.clear();
   }
 
   @override
   JS.Statement visitVariableDeclarationStatement(
           VariableDeclarationStatement node) =>
       _expressionStatement(_visit(node.variables));
 
   @override
   visitConstructorName(ConstructorName node) {
-    var typeName = _visit(node.type.name);
+    var typeName = _visit(node.type);
     if (node.name != null) {
       return js.call(
           '#.#', [typeName, _jsMemberName(node.name.name, isStatic: true)]);
     }
     return typeName;
   }
 
   @override
   visitInstanceCreationExpression(InstanceCreationExpression node) {
     return js.call(
@@ skipping 495 matching lines @@
     _catchParameter = savedCatch;
     return new JS.Catch(catchVarDecl, new JS.Block([catchBody]));
   }
 
   JS.Statement _catchClauseGuard(CatchClause clause, JS.Statement otherwise) {
     var then = visitCatchClause(clause);
 
     // Discard following clauses, if any, as they are unreachable.
     if (clause.exceptionType == null) return then;
 
+    // TODO(jmesserly): this is inconsistent with [visitIsExpression], which
+    // has special case for typeof.
     return new JS.If(js.call('dart.is(#, #)', [
       _visit(_catchParameter),
       _emitTypeName(clause.exceptionType.type),
     ]), then, otherwise);
   }
 
   JS.Statement _statement(Iterable stmts) {
     var s = stmts is List ? stmts : new List<JS.Statement>.from(stmts);
     // TODO(jmesserly): empty block singleton?
     if (s.length == 0) return new JS.Block([]);
@@ skipping 495 matching lines @@
 
     // TODO(jmesserly): in many cases marking the end will be unncessary.
     printer.mark(_location(node.end));
   }
 
   String _getIdentifier(AstNode node) {
     if (node is SimpleIdentifier) return node.name;
     return null;
   }
 }