[GHC] #13908: sameMutableArray equivalent for Array

[GHC]

#13908: sameMutableArray equivalent for Array
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        Reporter:  winter            |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3697
       Wiki Page:                    |
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Comment (by simonpj):

 I'm really not sure about this.  Mutable arrays have ''identity'' so it
 makes sense to ask if they are "the same".  Immutable arrays do not.  Are
 the two lists `[2,3]` and `[2,3]` "the same"?  Would it make a difference
 if you let-bound it `let x = [2,3] in sameList x x`?

 We have `unsafePtrEq` and `reallyUnsafePtrEq`.  Maybe use them instead?
 The danger is that legitimate compiler optimisations might change
 behaviour.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13908#comment:6>
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