Typechecker tests failures

[Simon Peyton Jones]

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 at gmail.com]
|  Sent: 08 December 2014 05:48
|  To: Simon Peyton Jones
|  Cc: ghc-devs at 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 <simonpj at microsoft.com>
|  > 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
|  >
|  >
|