[GHC] #8262: Ill-kinded value is not rejected immediately

10 Sep 2013

      #8262: Ill-kinded value is not rejected immediately
-------------------------------------+-------------------------------------
       Reporter:  monoidal           |             Owner:
           Type:  bug                |            Status:  new
       Priority:  low                |         Milestone:
      Component:  Compiler (Type     |           Version:  7.7
  checker)                           |  Operating System:  Unknown/Multiple
       Keywords:                     |   Type of failure:  GHC accepts
   Architecture:  Unknown/Multiple   |  invalid program
     Difficulty:  Unknown            |         Test Case:
     Blocked By:                     |          Blocking:
Related Tickets:                     |
-------------------------------------+-------------------------------------
 The expression `Just (1#)` is ill-kinded, since `Just` expects a parameter
 of type `a :: *` not `#`. GHC 7.6.3 recognizes this

 {{{
 λ> :t Just (1#)

 <interactive>:1:7:
     Couldn't match kind `*' against `#'
     Kind incompatibility when matching types:
       a0 :: *
       GHC.Prim.Int# :: #
     In the first argument of `Just', namely `(1#)'
     In the expression: Just (1#)
 }}}

 while HEAD gives

 {{{
 λ> :t Just (1#)
 Just (1#) :: a ~ GHC.Prim.Int# => Maybe a
 }}}

 Not a big deal, attempting to do anything with this value gives the same
 error as in 7.6.3. But still, I think it should be rejected as ill-kinded
 at sight.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8262
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler