GHCi panics due to linkSomeBCOs: no break array with 9.0.1
Summary
ghci-9.0.1 panics with linkSomeBCOs: no break array
when defining an instance for the following type class in the REPL:
module Foo (Foo(..)) where
class Foo a where
bar :: a -> ()
bar _ = ()
I came across this issue in https://github.com/maoe/influxdb-haskell/pull/85 and the snippet above is the result of code minimization.
Steps to reproduce
- Save the snippet in the summary as
Foo.hs
- Load it in GHCi and define the following instance in the REPL:
% ghci-9.0.1 Foo.hs
GHCi, version 9.0.1: https://www.haskell.org/ghc/ :? for help
[1 of 1] Compiling Foo ( Foo.hs, interpreted )
Ok, one module loaded.
ghci> data T = T
ghci> instance Foo T
ghc: panic! (the 'impossible' happened)
(GHC version 9.0.1:
linkSomeBCOs: no break array
Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug
If I delete the default implementation of the method bar, the issue disappears.
Expected behavior
It should just work like 8.10.4:
% ghci-8.10.4 Foo.hs
GHCi, version 8.10.4: https://www.haskell.org/ghc/ :? for help
[1 of 1] Compiling Foo ( Foo.hs, interpreted )
Ok, one module loaded.
*Foo> data T = T
*Foo> instance Foo T
*Foo>
Environment
- GHC version used: 9.0.1 installed with ghcup
- Operating System: macOS 11.2.1 (Big Sur)
- System Architecture: Intel