Fixes in codegen and test script

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;
 import 'dart:io' show Directory, File;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
@@ skipping 1519 matching lines @@
   }
 
   @override
   JS.Statement visitCatchClause(CatchClause node) {
     var body = [];
 
     var savedCatch = _catchParameter;
     if (node.catchKeyword != null) {
       var name = node.exceptionParameter;
       if (name != null && name.name != _catchParameter) {
-        body.add(js.statement('let # = #;', [_visit(name), _catchParameter]));
+        var decl = new JS.VariableDeclaration(name.name);
+        decl.sourceInformation = name;
+        body.add(js.statement('let # = #;', [decl, _catchParameter]));
         _catchParameter = name.name;
       }
       if (node.stackTraceParameter != null) {
         var stackVar = node.stackTraceParameter.name;
         body.add(js.statement(
             'let # = dart.stackTrace(#);', [stackVar, _visit(name)]));
       }
     }
 
     body.add(_visit(node.body));
@@ skipping 486 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;
   }
 }