blob: 7a9f410d64fa898008716f40e193796c8def90ec (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
|
{-# LANGUAGE MagicHash #-}
-- Type checking with unboxed kinds fails when (->) is used in a prefix way
module ShouldSucceed where
import GHC.Base
f :: (->) Int# Int#
f x = x
-- Here's the comment from TypeRep:
--
-- funTyCon = mkFunTyCon funTyConName
-- (mkArrowKinds [liftedTypeKind, liftedTypeKind]
-- liftedTypeKind)
-- You might think that (->) should have type (? -> ? -> *), and you'd be right
-- But if we do that we get kind errors when saying
-- instance Control.Arrow (->)
-- becuase the expected kind is (*->*->*). The trouble is that the
-- expected/actual stuff in the unifier does not go contra-variant, whereas
-- the kind sub-typing does. Sigh. It really only matters if you use (->) in
-- a prefix way, thus: (->) Int# Int#. And this is unusual.
|
