[GHC] #15694: GHC panic from pattern synonym, "Type-correct unfilled coercion hole"

[GHC]

#15694: GHC panic from pattern synonym, "Type-correct unfilled coercion hole"
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           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.6.1
           Keywords:                 |  Operating System:  Unknown/Multiple
  PatternSynonyms                    |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 {{{#!hs
 {-# Language RankNTypes, PatternSynonyms, TypeOperators, DataKinds,
 PolyKinds, KindSignatures, GADTs #-}

 import Data.Kind
 import Data.Type.Equality

 data Ctx :: Type -> Type where
  E     :: Ctx(Type)
  (:&:) :: a -> Ctx(as) -> Ctx(a -> as)

 data ApplyT(kind::Type) :: kind ->  Ctx(kind) -> Type where
  AO :: a -> ApplyT(Type) a E
  AS :: ApplyT(ks)      (f a) ctx
     -> ApplyT(k -> ks) f     (a:&:ctx)

 pattern ASSO :: () => forall ks k (f :: k -> ks) (a1 :: k) (ctx :: Ctx ks)
 (ks1 :: Type) k1 (a2 :: k1) (ctx1 :: Ctx ks1) a3. (kind ~ (k -> ks), a ~~
 f, b ~~ (a1 :&: ctx), ks ~ (k1 -> ks1), ctx ~~ (a2 :&: E), ks1 ~ Type, f
 a1 a2 ~~ a3) => a3 -> ApplyT kind a b
 pattern ASSO a = AS (AS (AO a))
 }}}

 {{{
 baldur at KindStar:~/hs$ ghci -ignore-dot-ghci 465.hs
 GHCi, version 8.7.20180828: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( 465.hs, interpreted )
 WARNING: file compiler/types/TyCoRep.hs, line 2378
   in_scope InScope {kind_a1Cw a_a1Cx b_a1Cy ks_a1Cz k_a1CA f_a1CB
                     a1_a1CC ctx_a1CD ks1_a1CE k1_a1CF a2_a1CG ctx1_a1CH
 a3_a1CI
                     k0_a1F8}
   tenv [a1Cw :-> kind_a1Cw[sk:0], a1Cx :-> a_a1Cx[sk:0],
         a1Cy :-> b_a1Cy[sk:0], a1Cz :-> ks_a1Cz[sk:0],
         a1CA :-> k_a1CA[sk:0], a1CB :-> f_a1CB[sk:0],
         a1CC :-> a1_a1CC[sk:0], a1CD :-> ctx_a1CD[sk:0],
         a1CE :-> ks1_a1CE[sk:0], a1CF :-> k1_a1CF[sk:0],
         a1CG :-> a2_a1CG[sk:0], a1CH :-> ctx1_a1CH[sk:0],
         a1CI :-> a3_a1CI[sk:0]]
   cenv []
   tys [kind_a1Cw[sk:1] ~ (k_a1CA[sk:2] -> ks_a1Cz[sk:2]),
        a_a1Cx[sk:1] ~~ f_a1CB[sk:2],
        b_a1Cy[sk:1] ~~ (a1_a1CC[sk:2] ':&: ctx_a1CD[sk:2]),
        ks_a1Cz[sk:2] ~ (k1_a1CF[sk:2] -> ks1_a1CE[sk:2]),
        ctx_a1CD[sk:2] ~~ (a2_a1CG[sk:2] ':&: 'E), ks1_a1CE[sk:2] ~ *,
        (f_a1CB[sk:2] a1_a1CC[sk:2] |> {co_a1Fc}) a2_a1CG[sk:2]
        ~~ a3_a1CI[sk:2]]
   cos []
   needInScope [a1F8 :-> k0_a1F8[sk:2], a1Fc :-> co_a1Fc]
 WARNING: file compiler/types/TyCoRep.hs, line 2378
   in_scope InScope {kind_a1Cw a_a1Cx b_a1Cy k0_a1HA ks_a1HB k_a1HC
                     f_a1HD a1_a1HE ctx_a1HF ks1_a1HG k1_a1HH a2_a1HI
 ctx1_a1HJ a3_a1HK}
   tenv [a1Cz :-> ks_a1HB[tau:4], a1CA :-> k_a1HC[tau:4],
         a1CB :-> f_a1HD[tau:4], a1CC :-> a1_a1HE[tau:4],
         a1CD :-> ctx_a1HF[tau:4], a1CE :-> ks1_a1HG[tau:4],
         a1CF :-> k1_a1HH[tau:4], a1CG :-> a2_a1HI[tau:4],
         a1CH :-> ctx1_a1HJ[tau:4], a1CI :-> a3_a1HK[tau:4],
         a1F8 :-> k0_a1HA[tau:4]]
   cenv []
   tys [kind_a1Cw[sk:0] ~ (k_a1CA[sk:0] -> ks_a1Cz[sk:0]),
        a_a1Cx[sk:0] ~~ f_a1CB[sk:0],
        b_a1Cy[sk:0] ~~ (a1_a1CC[sk:0] ':&: ctx_a1CD[sk:0]),
        ks_a1Cz[sk:0] ~ (k1_a1CF[sk:0] -> ks1_a1CE[sk:0]),
        ctx_a1CD[sk:0] ~~ (a2_a1CG[sk:0] ':&: 'E), ks1_a1CE[sk:0] ~ *,
        (f_a1CB[sk:0] a1_a1CC[sk:0] |> {co_a1Fc}) a2_a1CG[sk:0]
        ~~ a3_a1CI[sk:0]]
   cos []
   needInScope [a1Cw :-> kind_a1Cw[sk:0], a1Cx :-> a_a1Cx[sk:0],
                a1Cy :-> b_a1Cy[sk:0], a1Fc :-> co_a1Fc]
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.7.20180828 for x86_64-unknown-linux):
         ASSERT failed!
   Type-correct unfilled coercion hole {co_a1Fc}
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in
 ghc:Outputable
         pprPanic, called at compiler/utils/Outputable.hs:1219:5 in
 ghc:Outputable
         assertPprPanic, called at compiler/typecheck/TcHsSyn.hs:1716:99 in
 ghc:TcHsSyn

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

 >
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15694>
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