GHCi panics due to linkSomeBCOs: no break array with 9.0.1
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
- 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.
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>
- GHC version used: 9.0.1 installed with ghcup
- Operating System: macOS 11.2.1 (Big Sur)
- System Architecture: Intel