[GHC] #11451: Inconsistent warnings for unused binders in type and instance declarations

[GHC]

#11451: Inconsistent warnings for unused binders in type and instance declarations
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        Reporter:  simonpj           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I'd be willing to implement this, but let me make sure I understand what's
 being proposed. My understanding is that:

 * `-Wunused-matches` should no longer warn about unused type variables.
 Instead, a different flag (I propose `-Wunused-type-variables`) should
 trigger this separately.
 * `-Wunused-type-variables` shouldn't be enabled when `-Wall` is on. (Do
 we want a `-pedantic` flag which implies `-Wunused-type-variables`?)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11451#comment:21>
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