fixed a regression that for-in was failing to cache the source value

test/test_classes.coffee

@@ -182,7 +182,7 @@ class Mini
         @num
 
 m = new Mini
-ok (func() for func in m.generate()).join(' ') is '10 10 10'
+eq (func() for func in m.generate()).join(' '), '10 10 10'
 
 
 # Testing a contructor called with varargs.

test/test_comprehensions.coffee

@@ -101,3 +101,6 @@ learn = ->
 ok learn().join(' ') is '1 2 3'
 
 ok rule(101) is 101
+
+f = -> [-> ok no, 'should cache source']
+ok yes for k of [f] = f()