GHC HEAD regression: piResultTys1
The following program typechecks on GHC 8.0.2 through 8.6.3, but panics on HEAD:
{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeInType #-}
module Bug where
import Data.Kind
data T f :: f Type -> Type where
MkT :: T f a$ ~/Software/ghc4/inplace/bin/ghc-stage2 Bug.hs
[1 of 1] Compiling Bug ( Bug.hs, Bug.o )
ghc-stage2: panic! (the 'impossible' happened)
(GHC version 8.7.20190219 for x86_64-unknown-linux):
piResultTys1
k_a10k[tau:1]
[*]
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/utils/Outputable.hs:1159:37 in ghc:Outputable
pprPanic, called at compiler/types/Type.hs:1063:5 in ghc:Type