tests: remove extra_files.py (#12223)
[ghc.git] / testsuite / tests / typecheck / should_fail / SilentParametersOverlapping.hs
1 {-# LANGUAGE FlexibleInstances, FlexibleContexts, UndecidableInstances #-}
2
3 module SilentParametersOverlapping where
4
5 class C a where
6 c :: a -> ()
7
8 class C a => B a where
9 b :: a -> ()
10
11 instance C [a] where
12 c x = ()
13
14 instance {- silent: C [(a,b)] => -} B [(a,b)] where
15 b x = c [(undefined,undefined)]
16 -- We get wanted: C [(gamma, delta)],
17 -- and gamma,delta are unconstrained
18 -- We can apply the C [a] instance without difficulty, but
19 -- that fails due to silent dfun parameters