GHC panics on pattern synonym ‘kindPrimRep’
{-# Language PatternSynonyms, GADTs #-}
data Ty a where
B :: Ty Bool
class (Eq a, Ord a, Show a) => GetTy a where
getTy :: Ty a
instance GetTy Bool where
getTy = B
data Exp a where
Constant :: GetTy a => Ty a -> a -> Exp a
pattern MkBool :: () => (GetTy t, Bool ~ t) => t -> Exp t
pattern MkBool bool = Constant B bool
pattern Tru :: () => Bool ~ t => Exp t
pattern Tru = MkBool True
with head:
$ ghci -ignore-dot-ghci /tmp/tywM.hs
GHCi, version 8.1.20160503: http://www.haskell.org/ghc/ :? for help
[1 of 1] Compiling Main ( /tmp/tywM.hs, interpreted )
ghc: panic! (the 'impossible' happened)
(GHC version 8.1.20160503 for x86_64-unknown-linux):
kindPrimRep.go rep_a2tC
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
>
pattern Tru :: () => Bool ~ t => Exp t
pattern Tru = Constant B True
works fine
Trac metadata
Trac field | Value |
---|---|
Version | 8.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | mpickering |
Operating system | |
Architecture |