[GHC] #15035: Panic when using StaticPointers with typed holes

[GHC]

#15035: Panic when using StaticPointers with typed holes
-------------------------------------+-------------------------------------
           Reporter:  utdemir        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.4.1
           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:
-------------------------------------+-------------------------------------
 Adding a type hole when there is a type variable in `StaticPtr` throws a
 GHC panic:

 {{{#!hs
 {-# LANGUAGE StaticPointers #-}

 module Foo where

 import Data.Typeable
 import GHC.StaticPtr

 foo :: Typeable a => StaticPtr a
 foo = static _
 }}}

 {{{

 [1 of 1] Compiling Foo              ( test.hs, test.o )

 test.hs:9:14: error:ghc: panic! (the 'impossible' happened)
   (GHC version 8.4.1 for x86_64-unknown-linux):
         No skolem info:
   [a_aD2[sk:2]]
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in
 ghc:Outputable
         pprPanic, called at compiler/typecheck/TcErrors.hs:2945:5 in
 ghc:TcErrors

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 This panics on both GHC 8.2.2 and 8.4.1.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15035>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler