[GHC] #16127: Panic: piResultTys1 in compiler/types/Type.hs:1022:5

[GHC]

#16127: Panic: piResultTys1 in compiler/types/Type.hs:1022:5
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        Reporter:  _deepfire         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.6.1
  checker)                           |
      Resolution:                    |             Keywords:
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 simonpj):

 What to do?  The real problem is that if `A.hs` defines a type `T`
 differently than `A.hs-boot`, then anything imported into `A` whose type
 or kind mentions `T` is going to be ill-kinded.

 So I think the Right Thing is

 * Immediately after typechecking a type/class declaration `T`, check if
 there is a hs-boot file definition for it; if so, compare, and fail if
 there is a mis-match.

 Currently the hs-boot file comparison happens all at the end, so this
 would require a little re-plumbing.

 But before doing that, let's check that everyone agrees.  (Now that we
 know the cause, it should be easy to make an even simpler repro case.)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16127#comment:9>
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