(scrutinizer) Types for global variables are not refined by predicates

[megane]

(: g1 (list-of fixnum))
(define g1 '())
;; Aliased global gets refined
(let ((a g1))
  (compiler-typecase a ((list-of fixnum) 1))
  (if (null? a)
      (compiler-typecase a (null 1))
      (compiler-typecase a ((not null) 1))))

(: g2 (list-of fixnum))
(define g2 '())
(if (null? g2)
    (compiler-typecase g2 (null 1)) ;; <- error
    (compiler-typecase g2 ((pair fixnum (list-of fixnum)) 1)))

;; $ csc -O3 globals.scm
;; 
;; Error: at toplevel:
;;   (globals.scm:13) no clause applies in `compiler-typecase' for expression of type `(list-of fixnum)':
;;     null

I don't think this is an issue of non-local mutation (e.g. from other threads). You should use mutexes or some other measures to prevent mutation while, you're working on a global.

[megane]

Forgot to mention that I have a patch for this, if you think this should be fixed.

[sjamaan]

Getting ready for 5.1, moving tickets which won't make it in to 5.2.

[felix winkelmann]

You can only assume that "null" is valid for g2 directly after the predicate test - any global procedure call between predicate and use could jump back via a continuation, making the assumption invalid. I don't recall, whether the scrutinizer takes this into account. Does it? If yes, then I thunk your request makes sense.

[megane]

Not for 5.2