ghc panic: runtimeRepLevity_maybe
Summary
An ill-typed program triggers a panic while printing an error message.
Steps to reproduce
Compile this:
module Bug where
import GHC.Exts (TYPE)
data T (a :: TYPE r) = MkT
f :: T @(f a b) () -> ()
f MkT = ()
GHC tries to print an error message (as can be seen from the error code GHC-83865
) but then panics:
Bug.hs:7:17: error: [GHC-83865]ghc: panic! (the 'impossible' happened)
GHC version 9.7.20230110:
runtimeRepLevity_maybe
'BoxedRep
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/GHC/Utils/Panic.hs:189:37 in ghc:GHC.Utils.Panic
pprPanic, called at compiler/GHC/Core/Type.hs:796:22 in ghc:GHC.Core.Type
Expected behavior
A proper error message.
Environment
- GHC version used: HEAD.