[GHC] #14951: SpecContsr needs two runs when one should suffice

[GHC]

#14951: SpecContsr needs two runs when one should suffice
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  SpecConstr
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14844            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by nomeata):

 See `wip/T14951` for what I have in mind. If fixes the problem with the
 example code in the ticket.

 > BTW, what is the connection to the title of the ticket? Why does two
 runs help?

 Ah, right: If you simplify, then `l` gets inlined, and suddenly the body
 of `foo` _does_ scrutinize `t` and a second run of !SpecConstr would
 specialize `l`.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14951#comment:7>
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