GHC panic with TypeInType and type family
This rather simple type family,
{-# LANGUAGE TypeFamilies, TypeOperators, TypeInType #-}
module GenWhoops where
import GHC.Generics
type family GenComp k (x :: k) (y :: k) :: Ordering where
GenComp ((x :+: y) p) ('L1 x) ('L1 y) = GenComp (x p) x y
produces the following panic:
ghc-stage2: panic! (the 'impossible' happened)
(GHC version 8.3.20170828 for x86_64-unknown-linux):
piResultTy
k_a1LK[tau:1]
p_a1Lz[sk:1]
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/utils/Outputable.hs:1138:37 in ghc:Outputable
pprPanic, called at compiler/types/Type.hs:949:35 in ghc:Type
This happens with both GHC 8.2.1 and something very close to HEAD.
Trac metadata
Trac field | Value |
---|---|
Version | 8.2.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | goldfire |
Operating system | |
Architecture |