[GHC] #12159: Record-like GADTs with repeated fields (of same type) rejected

[GHC]

#12159: Record-like GADTs with repeated fields (of same type) rejected
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        Reporter:  heisenbug         |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by adamgundry):

 * cc: adamgundry (added)
 * type:  bug => feature request


Comment:

 It probably wouldn't be difficult to generate selector functions in cases
 like this, but record updates are likely to be tricky, because of cases
 like this:
 {{{#!hs
 data Foo p where
   Bar :: { quux :: a } -> Foo a
   Baz :: { quux :: a } -> Foo [a]
 }}}
 Record updates are already quite tricky to type-check. We'd need a clear
 specification of what should be accepted (see also #2595).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12159#comment:2>
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