[GHC] #10635: -fwarn-redundant-constraints should not be part of -Wall

[GHC]

#10635: -fwarn-redundant-constraints should not be part of -Wall
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        Reporter:  Lemming           |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  7.11
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9939, #9973,     |  Differential Rev(s):
  #10100, #10183                     |
       Wiki Page:                    |
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Comment (by Lemming):

 Replying to [comment:8 Lemming]:
 > If would prefer to disable the warning per constraint. E.g. I could wrap
 a not strictly needed constraint in a magic {{{Used :: Constraint ->
 Constraint}}}. However, this would not be possible in Haskell 98.

 A Haskell 98 compliant pragma might look like this:
 {{{#!hs
 {-# MINIMAL_CONSTRAINTS singleton () #-}
 singleton :: Ord a => a -> Set a
 }}}

 The pragma means: Type check "singleton" two times, once with the
 constraints `()` and once with the constraint `Ord a`. Warn about
 redundant constraints in the pragma but not in the signature of
 `singleton`.

 If you also want to warn about not maximally general types, then the
 pragma should even mention the whole type signature, e.g.
 {{{#!hs
 {-# MOST_GENERAL singleton :: a -> Set a #-}
 singleton :: Ord a => a -> Set a

 {-# MOST_GENERAL asTypeOf :: a -> b -> a #-}
 asTypeOf :: a -> a -> a
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10635#comment:9>
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