Handling FileError results in non-exhaustive matches

[cerk]

Here is a silly function that wraps coalton-library/file:exists? to produce a Boolean.

(coalton-toplevel
  (declare my-file-exists? (String -> Boolean))
  (define (my-file-exists? filename)
    (match (coalton-library/file:exists? filename)
      ((Err e) (progn
                 (match e
                   ((coalton-library/file:FileError _) (print "file error")))
                 False))
      ((Ok b) b))))

When I execute this in the REPL, I get non-exhaustive match warnings involving coalton-library/file::PathError, coalton-library/file::LispError and coalton-library/file::EOF.

To make the warnings go away, I can change the function to:

(coalton-toplevel
  (declare my-file-exists? (String -> Boolean))
  (define (my-file-exists? filename)
    (match (coalton-library/file:exists? filename)
      ((Err e) (progn
                 (match e
                   ((coalton-library/file:FileError _) (print "file error"))
                   ((coalton-library/file::PathError _ _) (print "path error"))
                   ((coalton-library/file::LispError _) (print "lisp error"))
                   ((coalton-library/file::EOF) (print "eof")))
                 False))
      ((Ok b) b))))

Are PathError, LispError and EOF not exported when they should be? Or should I ignore the non-exhaustive match warnings?

[garlic0x1]

Those symbols should be exported yes, fixed it here: #1647.

If you have the function you want, you can also just use the branch (_ (print "something else")) which will catch everything and make the match exhaustive.

Also just a tip: you don't need a progn in match branches.