Improve error messages around kind mismatches.
[ghc.git] / testsuite / tests / typecheck / should_fail / tcfail154.hs
1 {-# LANGUAGE MultiParamTypeClasses #-}
2
3 module ShouldFail where
4
5 data T a = MkT
6
7 class C a b where
8 op :: T a -> T b -> Bool
9
10 -- Repeated type variable in an instance constraint
11 -- should require UndecidableInstances
12 instance C a a => Eq (T a) where
13 (==) = op