[GHC] #14822: -XQuantifiedConstraints: Turn term-level entailments (:-) into constraints (=>)

GHC ghc-devs at haskell.org
Fri Feb 23 23:34:20 UTC 2018


#14822: -XQuantifiedConstraints: Turn term-level entailments (:-) into constraints
(=>)
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.5
      Resolution:  invalid           |             Keywords:
                                     |  QuantifiedConstraints, wipT2893
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by RyanGlScott):

 * status:  new => closed
 * resolution:   => invalid


Comment:

 I fully agree with kcsongor's analysis. This is essentially asking for a
 way to violate the open-world assumption, which isn't going to fly. If you
 want to use `(SBoolI b, SBoolI b') => Funny b b'` as a quantified
 constraint, then write an instance for it.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14822#comment:2>
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