[GHC] #12595: Linker failure: multiple definition of

[GHC]

#12595: Linker failure: multiple definition of
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        Reporter:  MikolajKonarski   |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
 Type of failure:  GHC rejects       |  (amd64)
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10531            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"2fbfbca2d12a8e9a09627529cf4f8284b19023ff/ghc"
 2fbfbca2/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="2fbfbca2d12a8e9a09627529cf4f8284b19023ff"
 Fix desugaring of pattern bindings (again)

 This patch fixes Trac #12595.  The problem was with a
 pattern binding like
      !x = e
 For a start it's silly to match that pattern and build
 a unit tuple (the General Case of mkSelectorBinds); but
 that's what was happening because the bang fell through
 to the general case.  But for a variable pattern building
 any auxiliary bindings is stupid.  So the patch
 introduces a new case in mkSelectorBinds for variable
 patterns.

 Then it turned out that if 'e' was a plain variable, and
 moreover was imported GlobalId, then matchSinglePat made
 it a /bound/ variable, which should never happen.  That
 ultimately caused a linker error, but the original bug
 was much earlier.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12595#comment:5>
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