Original bug ID: 7692
Reporter: @dra27
Assigned to: @garrigue
Status: assigned (set by @dra27 on 2017-12-19T11:36:25Z)
Resolution: open
Priority: normal
Severity: minor
Version: 4.06.0
Target version: undecided
Category: typing
Monitored by: @nojb @gasche

Bug description

On my machine, the following snippet takes 12 seconds to type.

type _ t =
         | T : ('a t -> 'a) t
         | End : unit t

let rec process : type a . a t -> a = function
| T ->
    process
| End ->
    ()

let () =
  process T T T T T T T T T T T T T T T T T T T T
          (* 1.5 seconds *)
          T
          (* 3 seconds *)
          T
          (* 6 seconds *)
          T
          (* 12 seconds *)
          T
          (* and so forth... *)
          End

Additional information

This has obviously been reduced from a much larger script (it would even be useful, if it didn't take 30 minutes to type it!).

(I realise that it's possible that this is simply a pattern which will always be difficult to type)