Higher-rank kind ascription oddities
GHC accepts these two definitions:
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeInType #-}
module Bug where
import Data.Proxy
f :: forall (x :: forall a. a -> Int). Proxy x
f = Proxy
g :: forall (x :: forall a. a -> Int). Proxy (x :: forall b. b -> Int)
g = Proxy
However, it does not accept this one, which (AFAICT) should be equivalent to the two above:
h :: forall x. Proxy (x :: forall b. b -> Int)
h = Proxy
GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
[1 of 1] Compiling Bug ( Bug.hs, interpreted )
Bug.hs:13:23: error:
• Expected kind ‘forall b. b -> Int’, but ‘x’ has kind ‘k0’
• In the first argument of ‘Proxy’, namely
‘(x :: forall b. b -> Int)’
In the type signature:
h :: forall x. Proxy (x :: forall b. b -> Int)
|
13 | h :: forall x. Proxy (x :: forall b. b -> Int)
| ^
Trac metadata
Trac field | Value |
---|---|
Version | 8.2.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |