[GHC] #11648: assertPprPanic, called at compiler/types/TyCoRep.hs:1932

[GHC]

#11648: assertPprPanic, called at compiler/types/TyCoRep.hs:1932
-------------------------------------+-------------------------------------
           Reporter:  thomie         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 As mentioned in https://mail.haskell.org/pipermail/ghc-
 devs/2016-February/011455.html, the following tests currently hit an
 assert when the compiler is built with -DDEBUG:

 {{{
    patsyn/should_compile  MoreEx [exit code non-0] (normal)
    patsyn/should_compile  T11224b [exit code non-0] (normal)
    polykinds              MonoidsTF [exit code non-0] (normal)
    polykinds              T11480b [exit code non-0] (normal)
    polykinds              T11523 [exit code non-0] (normal)
 }}}

 {{{
 Compile failed (status 256) errors were:
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.1.20160218 for x86_64-unknown-linux):
 ASSERT failed!
   CallStack (from HasCallStack):
   assertPprPanic, called at compiler/types/TyCoRep.hs:1932:56 in
 ghc:TyCoRep
   checkValidSubst, called at compiler/types/TyCoRep.hs:1991:17 in
 ghc:TyCoRep
   substTys, called at compiler/types/TyCoRep.hs:2012:14 in ghc:TyCoRep
   substTheta, called at compiler/typecheck/TcPatSyn.hs:255:20 in
 ghc:TcPatSyn
   in_scope InScope {d_ap0 c_apv}
   tenv [ap1 :-> c_apv[tau:5]]
   tenvFVs [aps :-> t_aps[tau:1], apv :-> c_apv[tau:5]]
   cenv []
   cenvFVs []
   tys []
   cos []
 }}}

 Phab:D1951 contained a stopgap patch, but since it wasn't accepted, I'll
 just mark the tests as expect_broken for this ticket, so that other
 developers aren't bothered by this issue.

 The offending commit is b5292557dcf2e3844b4837172230575d40a8917e.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11648>
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