initTc: unsolved constraints
Prelude> lucky (7.0 :: Num)
ghc.exe: panic! (the 'impossible' happened)
(GHC version 8.0.2 for x86_64-unknown-mingw32):
initTc: unsolved constraints
WC {wc_insol =
[W] lucky_afgR :: t_afgQ[tau:1] (CHoleCan: lucky)
[W] lucky_afhl :: t_afhk[tau:1] (CHoleCan: lucky)}
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
lucky :: Num -> String
lucky 7 = "LUCKY NUMBER SEVEN!"
lucky x = "Sorry, you're out of luck, pal!"
I believe that the function declaration and invocation above don't actually make sense, but they caused a panic that asked for a bug report so I'm doing it. Apologies for my newness :)