Richard
It's clearly wrong as it is, but I suggest you that you make tcSubsumes use captureConstraints rather than pushLevelAndCaptureConstratints. That's what solveEqualities does, after all.
Simon
| -----Original Message-----
| From: Richard Eisenberg [mailto:rae@cs.brynmawr.edu]
| Sent: 26 October 2017 23:12
| To: Simon Peyton Jones
| Cc: ghc-devs
| Subject: tcSubsumes
|
| Hi Simon,
|
| Could you take a look at TcSimplify.tcSubsumes? This relatively new
| function pushes the TcLevel when calling tcSubType, but then doesn't set
| the TcLevel when calling the solver. Inexplicably, this sometimes works -
| - even passing the testsuite. Somehow, my work caused this to fail. I
| fixed it by setting the TcLevel before calling the solver.
|
| Two questions:
|
| 1. Is this a reasonable fix?
|
| 2. (optional) How is it possible that this didn't fail drastically often?
|
| Note (to author / reviewers of this function): my astonishment isn't that
| this error crept into the codebase -- I've done similar many many times.
| My astonishment is how the testsuite didn't find this error forthwith.
|
| Thanks,
| Richard
