[GHC] #16154: -Wredundant-constraints: False positive

[GHC]

#16154: -Wredundant-constraints: False positive
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           Reporter:  fumieval       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.6.3
  (Type checker)                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Incorrect
  Unknown/Multiple                   |  error/warning at compile-time
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 GHC produces a warning for the attached source, although it won't compile
 if the suggested constraints are removed:

 {{{
 redundant-constraint.hs:24:1: warning: [-Wredundant-constraints]
     • Redundant constraints: (KnownNat 42, Capture 42 p)
     • In the type signature for:
            foo :: Foo 42
    |
 24 | foo :: Foo 42
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16154>
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