GHC issueshttps://gitlab.haskell.org/ghc/ghc/-/issues2019-07-07T18:14:23Zhttps://gitlab.haskell.org/ghc/ghc/-/issues/15076Typed hole with higher-rank kind causes GHC to panic (No skolem info)2019-07-07T18:14:23ZRyan ScottTyped hole with higher-rank kind causes GHC to panic (No skolem info)Spun out from #14040\#[ticket:15076\#comment:152359](https://gitlab.haskell.org//ghc/ghc/issues/15076#note_152359), which was different enough from the original program in #14040 to warrant its own ticket. The following program panics on...Spun out from #14040\#[ticket:15076\#comment:152359](https://gitlab.haskell.org//ghc/ghc/issues/15076#note_152359), which was different enough from the original program in #14040 to warrant its own ticket. The following program panics on every version of GHC from 8.0.2 onward:
```hs
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeInType #-}
module Bug where
import Data.Kind
import Data.Proxy
foo :: forall (a :: Type)
(f :: forall (x :: a). Proxy x -> Type).
Proxy f -> ()
foo (_ :: _) = ()
```
```
$ ~/Software/ghc/inplace/bin/ghc-stage2 Bug.hs
[1 of 1] Compiling Bug ( Bug.hs, Bug.o )
Bug.hs:12:11: error:ghc-stage2: panic! (the 'impossible' happened)
(GHC version 8.5.20180420 for x86_64-unknown-linux):
No skolem info:
[a_aZo[sk:1]]
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/utils/Outputable.hs:1162:37 in ghc:Outputable
pprPanic, called at compiler/typecheck/TcErrors.hs:3224:5 in ghc:TcErrors
```8.8.1