Incorrect variable lookup converted by datum->syntax

[Takashi Kato]

If an identifier is not bound the same level then it should not be the same. Following should raise an unbound error.

(define-syntax aif
  (lambda (x)
    (syntax-case x ()
      ((ng test then)
       #'(aif test then #f)) ;; template variable aif is not the same bound if (aif #t it)
      ((aif test then else)
       (with-syntax ((it (datum->syntax #'aif 'it)))
         #'(let ((it test))
             (if it then else)))))))
(aif #t it)

[Takashi Kato]

Changing er-rename not to lookup before renaming. Adding identifier identity slot to determine whether identifiers are the same bound or not. Adding different bound test case. Fixes #89 Fixes #92

→ <<cset 4f7dbb94ab8b>>