Printer for LET invokes sharing printing for NIL when *PRINT-CIRCLE* and *PRINT-PRETTY* are true

[Paul F. Dietz]

(in-package :cl-user)

(with-standard-io-syntax (let ((*print-pretty* t) (*print-circle* t)) (print '(let () (let () x))) (values)))

>> (LET #1=()
    (LET #1#
      X))

This does not happen if LET is replaced by a random symbol:

(with-standard-io-syntax (let ((*print-pretty* t) (*print-circle* t)) (print '(f () (f () x))) (values)))

>> (F NIL (F NIL X))

It does happen with some other standardized symbols (LET*, DOTIMES, PROG, for example).

[Paul F. Dietz (paul-f-dietz)]

Patch to fix the bug (ignore circularity detection on NIL).

[Stas Boukarev (stassats)]

9432d0bf9b614e30de564bcd8e71e796b9b05f53