[GHC] #14174: GHC panic with TypeInType and type family

[GHC]

#14174: GHC panic with TypeInType and type family
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.3
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"8b36ed129652df07af22b5e2a2e57b1df8cfbbc9/ghc" 8b36ed1/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="8b36ed129652df07af22b5e2a2e57b1df8cfbbc9"
 Build only well-kinded types in type checker

 During type inference, we maintain the invariant that every type is
 well-kinded /without/ zonking; and in particular that typeKind does
 not fail (as it can for ill-kinded types).

 But TcHsType.tcInferApps was not guaranteeing this invariant,
 resulting in Trac #14174 and #14520.

 This patch fixes it, making things better -- but it does /not/
 fix the program in Trac #14174 comment:5, which still crashes.
 So more work to be done.

 See Note [Ensure well-kinded types] in TcHsType
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14174#comment:6>
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