GHC panic from pattern synonyms + deferred type errors
{-# Language DataKinds, TypeOperators, PolyKinds, PatternSynonyms, GADTs #-}
{-# Options_GHC -dcore-lint -fdefer-type-errors #-}
import Data.Kind
data Ctx :: Type -> Type where
E :: Ctx(Type)
(:&:) :: a -> Ctx(as) -> Ctx(a -> as)
data ApplyT (k::Type) :: k -> Ctx(k) -> Type where
AO :: a -> ApplyT(Type) a E
AS :: ApplyT(ks) (f a) ctx
-> ApplyT(k -> ks) f (a:&:ctx)
pattern ASSO = AS (AS (AO False))
$ ghci -ignore-dot-ghci 463.hs
hs/463.hs:16:27: warning: [-Wdeferred-type-errors]
• Couldn't match type ‘a a1 a2’ with ‘Bool’
Expected type: a3
Actual type: Bool
• In the pattern: False
In the pattern: AO False
In the pattern: AS (AO False)
|
16 | pattern ASSO = AS (AS (AO False))
| ^^^^^
ghc-stage2: panic! (the 'impossible' happened)
(GHC version 8.7.20180828 for x86_64-unknown-linux):
urk! lookup local fingerprint
$mASSO
[iESflb :-> ($trModule, 1ca40dc83a9c879effdb760462cc9a2d),
iESgKD :-> ($tc'E, 79f67a27a14dc1bb6eecb39e4b061e2c),
iESgKF :-> ($tc':&:, 24793c0c1652ffcf92e04f47d38fa075),
iESgKH :-> ($tcCtx, a3f9358cbfe161bf59e75500d70ce0ae),
iESgKI :-> ($tc'AO, 72111d1891cb082e989c20a2191a8b4b),
iESgKK :-> ($tc'AS, ff019c04c400d5fbdd46ff8a816d4913),
iESgKM :-> ($tcApplyT, cbfe28374b4115925c7213e6330ab115)]
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable
pprPanic, called at compiler/iface/MkIface.hs:524:37 in ghc:MkIface
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
>
Trac metadata
Trac field |
Value |
Version |
8.6.1 |
Type |
Bug |
TypeOfFailure |
OtherFailure |
Priority |
normal |
Resolution |
Unresolved |
Component |
Compiler |
Test case |
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Differential revisions |
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BlockedBy |
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Related |
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Blocking |
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CC |
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Operating system |
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