blob: 9a5af411e2165cc0129fc6c7589c1d94477c5dbb (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
|
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE TypeFamilies #-}
module Bug where
import Data.Kind
class C (a :: k) where
type T k :: Type
-- This used to fail, with a mysterious error messate
-- Type indexes must match class instance head
-- Expected: T (a1 -> Either a1 b1)
-- Actual: T (a -> Either a b)
-- but now it succeeds fine
instance C Left where
type T (a -> Either a b) = Int
|
