fix memory leak cause by fat arrows: ref. jashkenas/coffeescript#3143

Author: michaelficarra

lib/compiler.js

@@ -646,10 +646,10 @@ class exports.Compiler
 
         fn = new JS.FunctionExpression null, parameters, block
         if performedRewrite
-          new JS.SequenceExpression [
-            new JS.AssignmentExpression '=', newThis, new JS.ThisExpression
-            fn
-          ]
+          new JS.CallExpression (memberAccess (new JS.FunctionExpression null, [], new JS.BlockStatement [
+            stmt new JS.AssignmentExpression '=', newThis, new JS.ThisExpression
+            new JS.ReturnStatement fn
+          ]), 'apply'), [new JS.ThisExpression, new JS.Identifier 'arguments']
         else fn
     ]
     [CS.Rest, ({expression}) -> {rest: yes, expression, isExpression: yes, isStatement: yes}]