[GHC] #7775: Mark intentionally omitted type class instances

[GHC]

#7775: Mark intentionally omitted type class instances
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        Reporter:  Lemming                  |            Owner:
            Type:  feature request          |           Status:  closed
        Priority:  normal                   |        Milestone:
       Component:  Compiler (Type checker)  |          Version:  7.7
      Resolution:  wontfix                  |         Keywords:  instance
Operating System:  Unknown/Multiple         |  warning
 Type of failure:  None/Unknown             |     Architecture:
       Test Case:                           |  Unknown/Multiple
        Blocking:                           |       Difficulty:  Unknown
                                            |       Blocked By:
                                            |  Related Tickets:
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Changes (by Lemming):

 * version:  7.6.2 => 7.7


Comment:

 There is still a difference between intentionally and unintentionally
 omitted instances. I find it important to document for me and for others
 why I have omitted an instance. Also without the "possible fix" message
 people keep asking why an obvious instance is missing. "Why is this parser
 not Monoid?" - maybe because there are different ways of viewing it as
 Monoid. "Why is this identifier type not Num?" - maybe because it makes no
 sense to multiply identifiers. Or even worse, people do not just ask but
 start writing (conflicting) orphan instances.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7775#comment:3>
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