[GHC] #10905: Incorrect number of parameters in "role" errors

[GHC]

#10905: Incorrect number of parameters in "role" errors
-------------------------------------+-------------------------------------
        Reporter:  crockeea          |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.2
      Resolution:                    |                Keywords:  roles
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by goldfire):

 I know what's going on here: GHC is reporting the role of //kind//
 parameters (which are all nominal). It shouldn't (unless you say `-fprint-
 explicit-kinds`, I think). Easy to fix.

 But Simon removed this role-signature-reporting code. From !TcErrors:

 {{{
 -- SLPJ Jun 15: I could not convince myself that these hints were really
 -- useful.  Maybe they are, but I think we need more work to make them
 -- actually helpful.
 }}}

 So the error is therefore absent in HEAD. But I thought those role
 signatures were helpful, and it sounds like @crockeea does too.

 So, Simon, care to elaborate on why you removed these? Are there too many
 signatures reported?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10905#comment:1>
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