[GHC] #14086: Empty case does not detect kinds

3 Aug 2017

      #14086: Empty case does not detect kinds
-------------------------------------+-------------------------------------
           Reporter:  dfeuer         |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  low            |         Milestone:  8.4.1
          Component:  Compiler       |           Version:  8.2.1
  (Type checker)                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Incorrect
  Unknown/Multiple                   |  error/warning at compile-time
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 {{{#!hs
 {-# language TypeInType, EmptyCase #-}
 module Silly where
 import Data.Kind

 f :: Type -> Int
 f x = case x of
 }}}

 GHC warns

 {{{
     Pattern match(es) are non-exhaustive
     In a case alternative: Patterns not matched: _ :: *
 }}}

 In fact, `Type` is only a type because of `TypeInType`. It has no actual
 values, so the empty case is exhaustive.

 To be honest, I kind of wish GHC would give me a warning for doing
 something so silly as to even give a function an argument of type `Type`,
 but I imagine that might be hard.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14086
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