Fixes #2274 -- allow @variables as loop variables

lib/coffee-script/grammar.js

@@ -413,7 +413,7 @@
       })
     ],
     ForValue: [
-      o('Identifier'), o('Array', function() {
+      o('Identifier'), o('ThisProperty'), o('Array', function() {
         return new Value($1);
       }), o('Object', function() {
         return new Value($1);

src/grammar.coffee

@@ -443,6 +443,7 @@ grammar =
   # This enables support for pattern matching.
   ForValue: [
     o 'Identifier'
+    o 'ThisProperty'
     o 'Array',                                  -> new Value $1
     o 'Object',                                 -> new Value $1
   ]

test/comprehensions.coffee

@@ -499,3 +499,14 @@ test "#2007: Return object literal from comprehension", ->
   eq 2, y.length
   eq 1, y[0].x
   eq 0, y[1].x
+  
+test "#2274: Allow @values as loop variables", ->
+  obj = {
+    item: null
+    method: ->
+      for @item in [1, 2, 3]
+        null
+  }
+  eq obj.item, null
+  obj.method()
+  eq obj.item, 3