[GHC] #15474: Error message mentions Any

3 Aug 2018

      #15474: Error message mentions Any
-------------------------------------+-------------------------------------
           Reporter:  monoidal       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  low            |         Milestone:  8.8.1
          Component:  Compiler       |           Version:  8.4.3
           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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 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?

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15474
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