Ticket #7197 (closed bug: duplicate)
ghc panic: Irrefutable pattern failed
I get following error, when trying to compile following snippet:
module BooleanFunction where class BooleanFunction a where arity :: a -> Int instance BooleanFunction Bool where arity _ = 0 instance BooleanFunction a => BooleanFunction Bool -> a where arity _ = 1 + arity a
[1 of 1] Compiling BooleanFunction ( BooleanFunction.hs, BooleanFunction.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.4.2 for x86_64-unknown-linux): compiler/rename/RnSource.lhs:430:14-81: Irrefutable pattern failed for pattern Data.Maybe.Just (inst_tyvars, _, SrcLoc.L _ cls, _) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
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