[GHC] #13610: Unhelpful error messages about lifted and unlifted types

[GHC]

#13610: Unhelpful error messages about lifted and unlifted types
-------------------------------------+-------------------------------------
        Reporter:  nomeata           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by nomeata):

 Ah, the problem is that `IO`’s type expects the second component of the
 tuple to be lifted, but `Weak#` is not. So the code is indeed bogus, but
 the error message is not very helpful.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13610#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler