[GHC] #8950: Typeable instances for promoted lists and tuples

[GHC]

#8950: Typeable instances for promoted lists and tuples
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        Reporter:  kosmikus          |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  libraries/base    |          Version:  7.8.1-rc2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by goldfire):

 How should we treat this:

 {{{
 data Foo = Bar

 deriving instance Typeable Foo
 deriving instance Typeable Bar
 }}}

 Is that an error (duplicate instance `Typeable Bar`)? Is it a warning?
 Silently ignored? What if the `deriving`s are in different modules?

 And, regardless of specific answers to the above, are we aiming for 7.8
 with this? That is, should I be rushing this, or can I get to it when I
 clump together some GHC tasks?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8950#comment:5>
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