[GHC] #9220: type roles for unboxed arrays

[GHC]

#9220: type roles for unboxed arrays
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              Reporter:  rwbarton    |            Owner:  goldfire
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:  Core        |          Version:  7.8.1
  Libraries                          |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by simonpj):

 Just to be clear, what exactly is "the fix" you mention?
  * What roles are you proposing for arrays of various sorts?
  * What goes wrong with the above instance?  Is it rejecting a program
 that is bogus, or is it rejecting a program that "ought" to be ok?

 Incidentally, I think it should ''definitely'' be part of the contract for
 `Storable` that `sizeOf` should return the same result for a newtype as
 for the type it wraps. Thus this would be BAD:
 {{{
 newtype N = MkN T

 instance Storable T where
   sizeOf _ = 4

 instance Storable N where
   sizeOf _ = 8
 }}}
 If `N` and `T` are representationally equaly, how could they take a
 different number of bytes to represent.  That should be part of the
 documentation for `Storable`.  I believe this is what Reid was saying in
 comment:8.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9220#comment:12>
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