[GHC] #13468: GHC stubbornly produces dead code for empty case with type family

[GHC]

#13468: GHC stubbornly produces dead code for empty case with type family
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"f0d98fc6cdde26bf43a04d9f01b6ad2f4c88f0b9/ghc" f0d98fc/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="f0d98fc6cdde26bf43a04d9f01b6ad2f4c88f0b9"
 Do Note [Improving seq] always

 This patch fixes Trac #13468, and at the same time makes the
 code simpler and more uniform.  In particular, I've eliminated
 the awkward conflict between the old built-in rule for seq
 (which elimianted a cast), and the desire to make case scrutinse
 a data type by doing type-family reduction (which adds a cast).

 Nice.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13468#comment:1>
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