[GHC] #15829: Add a test case for tricky type synonyms involving visible dependent kinds

29 Oct 2018

      #15829: Add a test case for tricky type synonyms involving visible dependent kinds
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           Reporter:  RyanGlScott    |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.8.1
          Component:  Compiler       |           Version:  8.7
  (Type checker)                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 This code does not typecheck on GHC 8.6.1:

 {{{#!hs
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE PolyKinds #-}
 module Bug where

 import Data.Kind

 data A :: Type -> Type
 data B a :: A a -> Type
 type C a = B a
 }}}

 However, it //does// typecheck on GHC HEAD, after commit
 5e45ad10ffca1ad175b10f6ef3327e1ed8ba25f3 (Finish fix for #14880.). This is
 very cool, although it does alarm me that there is no test case which
 checks for this at the moment. Let's add one to ensure that this stays
 fixed.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15829
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