Thanks. This was being tracked in Trac #9567, and I have finally gotten around to fixing it. Your proposed change is small, but it simply avoids the crash without fixing the cause. The cause was that contInputType was simply *wrong*. https://ghc.haskell.org/trac/ghc/ticket/9567 Fixed now! Simon | -----Original Message----- | From: Yuras Shumovich [mailto:shumovichy@gmail.com] | Sent: 08 December 2014 05:48 | To: Simon Peyton Jones | Cc: ghc-devs@haskell.org Devs | Subject: Re: Typechecker tests failures | | | Simon, | | I tracked T7891 and tc124 failure down to simplifier, namely | `simplExprF1` for `Case`. Core lint catches the bug (requires -O1 at | least), but without -dcore-lint compiler hangs in busy loop. I made it | work with simple patch: | | > diff --git a/compiler/simplCore/Simplify.hs | > b/compiler/simplCore/Simplify.hs index 7611f56..d396b60 100644 | > --- a/compiler/simplCore/Simplify.hs | > +++ b/compiler/simplCore/Simplify.hs | > @@ -950,8 +950,10 @@ simplExprF1 env expr@(Lam {}) cont | > zap b | isTyVar b = b | > | otherwise = zapLamIdInfo b | > | > -simplExprF1 env (Case scrut bndr _ alts) cont | > - = simplExprF env scrut (Select NoDup bndr alts env cont) | > +simplExprF1 env (Case scrut bndr alts_ty alts) cont | > + = do { expr <- simplExprC env scrut (Select NoDup bndr alts env | > + (mkBoringStop alts_ty)) | > + ; rebuild env expr cont } | > | > simplExprF1 env (Let (Rec pairs) body) cont | > = do { env' <- simplRecBndrs env (map fst pairs) | | (I have no idea what most of this code does, but I learned a lot while | investigating this issue :) ) | | The relevant commit is: | | > commit a0b2897ee406e24a05c41768a0fc2395442dfa06 | > Author: Simon Peyton Jones | > Date: Tue May 27 09:09:28 2014 +0100 | > | > Simple refactor of the case-of-case transform | > | > More modular, less code. No change in behaviour. | | The T7861 failed because additional lambda abstraction in Core. Not | sure whether it is important. | | Thanks, | Yuras | | On Sat, 2014-12-06 at 19:04 +0300, Yuras Shumovich wrote: | > Hello, | > | > I was working on #9605, and found a number of failed tests: | > | > Unexpected failures: | > should_compile T7891 [exit code non-0] (hpc,optasm,optllvm) | > should_compile tc124 [exit code non-0] (hpc,optasm,optllvm) | > should_run T7861 [bad exit code] | > (normal,hpc,optasm,ghci,threaded1,threaded2,dyn,optllvm) | > | > They seem to be unrelated to my work, and they are skipped when | "fast" | > is enabled. | > | > T7891 and tc124 fail with Core Lint errors. | > | > Looks like Phabricator uses "fast" way to validate revisions, so the | > failures were not noticed. | > | > Thanks, | > Yuras | > | > |