[GHC] #5267: Missing type checks for arrow command combinators

[GHC]

#5267: Missing type checks for arrow command combinators
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        Reporter:  peteg                        |            Owner:  ross
            Type:  bug                          |           Status:  new
        Priority:  low                          |        Milestone:  7.10.1
       Component:  Compiler (Type checker)      |          Version:  7.0.3
      Resolution:                               |         Keywords:
Operating System:  Unknown/Multiple             |     Architecture:
 Type of failure:  GHC accepts invalid program  |  Unknown/Multiple
       Test Case:                               |       Difficulty:
        Blocking:                               |       Blocked By:
                                                |  Related Tickets:
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"f50d62bb6c0357991fabf938bc971d528bbf5cc4/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="f50d62bb6c0357991fabf938bc971d528bbf5cc4"
 Fix the scope-nesting for arrows

 Previously we were capturing the *entire environment* when moving under
 a 'proc', for the newArrowScope/escapeArrowScope thing.  But that a
 blunderbuss,
 and in any case isn't right (the untouchable-type-varaible invariant gets
 invalidated).

 So I fixed it to be much more refined: just the LocalRdrEnv and
 constraints are
 captured.

 I think this is right; but if not we should just add more fields to
 ArrowCtxt,
 not return to the blunderbuss.

 This patch fixes the ASSERT failure in Trac #5267
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5267#comment:22>
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