(c)

USING: arrays kernel locals locals.parser locals.types
locals.rewrite.closures math prettyprint sequences quotations ;
IN: checks

<<

[let* | x [ "x" make-local ]
        b [ x [ 10 + ] x prefix 2array 1array ]
        le [ b x 1quotation <let*> dup . 1quotation ]
        la [ x 1array le 1quotation <lambda> dup . ] |
    la rewrite-closures first . ]

>>

! 'le [ b x 1quotation <let*> dup . ____1quotation____ ]'

(c) output

[let* | x [ x 10 + ] | x ]
[| x | [ [let* | x [ x 10 + ] | x ] ] ]

error:
...
You have found a bug in locals. Please report.
args [ ]
obj  x

so, my questions: 
1. (c) works fine, but (c) doesn't, why? where is a difference?

2. is (b) correct? if it is, why (c) doesn't work?