[GHC] #8566: Given kind equalities are discarded

[GHC]

#8566: Given kind equalities are discarded
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        Reporter:  dreixel           |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:  polykinds/T8566   |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by simonpj):

 That sounds difficult.  We can emit a warning when dropping a given kind
 equality; indeed, my proposal amounts to ensuring that no such warnings
 would be generated.  But to warn only if we drop a kind equality ''that
 would (later) be needed to make the program type check'' would be a lot
 harder.

 I suppose we could keep the kind-equality and complain only if it was
 used.  But being "used" is different to being "needed".

 Since you want to add full-on kind equalities, we should not over invest
 in this... let's just do something simple.  (Or even nothing.)

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8566#comment:14>
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