fixes #206, add checking for unary ops

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 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/src/generated/ast.dart' hide ConstantEvaluator;
@@ skipping 2143 matching lines @@
   visitRethrowExpression(RethrowExpression node) {
     if (node.parent is ExpressionStatement) {
       return js.statement('throw #;', _visit(_catchParameter));
     } else {
       return js.call('dart.throw_(#)', _visit(_catchParameter));
     }
   }
 
   @override
   JS.If visitIfStatement(IfStatement node) {
     return new JS.If(_visit(node.condition), _visit(node.thenStatement),

[vsm, 2015/06/04 17:07:32]

E.g., s/_visit(node.condition)/notNull(node.condition)/

or handle in checker?

[Jennifer Messerly, 2015/06/04 21:54:18]

Done.

         _visit(node.elseStatement));
   }
 
   @override
   JS.For visitForStatement(ForStatement node) {
     var init = _visit(node.initialization);
     if (init == null) init = _visit(node.variables);
     var update = _visitListToBinary(node.updaters, ',');
     if (update != null) update = update.toVoidExpression();
     return new JS.For(init, _visit(node.condition), update, _visit(node.body));
@@ skipping 289 matching lines @@
   ///       Point(x, y) {
   ///         this[_x] = x;
   ///         this[_y] = y;
   ///       }
   ///       get x() { return this[_x]; }
   ///       get y() { return this[_y]; }
   ///     }
   ///
   /// For user-defined operators the following names are allowed:
   ///
-  ///     <, >, <=, >=, ==, -, +, /, ˜/, *, %, |, ˆ, &, <<, >>, []=, [], ˜
+  ///     <, >, <=, >=, ==, -, +, /, ~/, *, %, |, ^, &, <<, >>, []=, [], ~
   ///
   /// They generate code like:
   ///
   ///     x['+'](y)
   ///
   /// There are three exceptions: [], []= and unary -.
   /// The indexing operators we use `get` and `set` instead:
   ///
   ///     x.get('hi')
   ///     x.set('hi', 123)
@@ skipping 165 matching lines @@
 
 /// A special kind of element created by the compiler, signifying a temporary
 /// variable. These objects use instance equality, and should be shared
 /// everywhere in the tree where they are treated as the same variable.
 class TemporaryVariableElement extends LocalVariableElementImpl {
   TemporaryVariableElement.forNode(Identifier name) : super.forNode(name);
 
   int get hashCode => identityHashCode(this);
   bool operator ==(Object other) => identical(this, other);
 }