Re: [GHC] #9858: Typeable instances should be kind-aware

3 Feb 2015

      #9858: Typeable instances should be kind-aware
-------------------------------------+-------------------------------------
        Reporter:  dreixel           |                   Owner:  dreixel
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.10.1
       Component:  Compiler          |                 Version:  7.9
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by goldfire):

 Replying to [comment:43 oerjan]:
...
It may be too weird to count as "existing code", but can it handle this?
Let's see.

 Everything is peachy until the second clause for `nest`. There, we assume
 `Typeable <k> a` (writing the implicit kind argument in angle brackets)
 and must produce `Typeable  *> (C <k> <k> a)`. I believe a
 sufficiently smart solver should be able to do this without difficulty. It
 will have access to fingerprint information for `k`, and should be able to
 build a fingerprint for `k -> *` from what it has. Good test case, but it
 seems workable with the proposed fix.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9858#comment:45
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler