Debugging specialization

Alexis King lexi.lambda at
Fri Oct 25 16:34:55 UTC 2019

> On Oct 25, 2019, at 04:07, Simon Peyton Jones <simonpj at> wrote:
> |  I’ve noticed that Specialise.hs has handful of pprTrace calls sprinkled
> |  about, but they are all commented out. Is the recommended method to just
> |  uncomment these calls and rebuild GHC?
> That's what I do.

Thanks, I did indeed end up doing this, and it was enough to diagnose my problem.

> But it would be better to stand back a bit and ask "what information would I really like to see?" and then design some logging mechanism to show it.  I'd be happy to advise.

It would be nice to have a -dspecialise-check in the same vein as the existing -dinline-check/-drule-check flags, which seems probably not too hard to add. I unfortunately can’t dedicate the time to add it myself right now, as I’ve solved my immediate problem and probably already sunk more time into this than I ought to, but if it comes up again and I can spare the time I might give it a shot.

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