[GHC] #15474: Error message mentions Any

[GHC]

#15474: Error message mentions Any
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        Reporter:  monoidal          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  low               |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Description changed by monoidal:

Old description:

> I'm not sure if this is a bug. File:
>
> {{{#!hs
> {-# LANGUAGE RankNTypes #-}
> {-# LANGUAGE TypeInType #-}
> module T15474 where
>
> import Data.Kind (Type)
>
> data Proxy a
>
> type Forall = forall t. Proxy t
>
> f1 :: forall (t :: Type). Proxy t
> f1 = f1
>
> f2 :: Forall
> f2 = f1
> }}}
>
> gives an error message mentioning Any:
>
> {{{
>     • Couldn't match type ‘GHC.Types.Any’ with ‘*’
>       Expected type: Proxy t
>         Actual type: Proxy t0
> }}}
>
> The appearance of Any is suspicious - I thought it's an implementation
> detail?

New description:

 I'm not sure if this is a bug. File:

 {{{#!hs
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TypeInType #-}
 module T15474 where

 import Data.Kind (Type)

 data Proxy a

 type Forall = forall t. Proxy t

 f1 :: forall (t :: Type). Proxy t
 f1 = f1

 f2 :: Forall
 f2 = f1
 }}}

 gives an error message mentioning Any:

 {{{
     • Couldn't match type ‘GHC.Types.Any’ with ‘*’
       Expected type: Proxy t
         Actual type: Proxy t0
 }}}

 The appearance of Any is suspicious to me - I thought it's an
 implementation detail?

--

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15474#comment:1>
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