[GHC] #11700: pattern match bug

[GHC]

#11700: pattern match bug
-------------------------------------+-------------------------------------
           Reporter:  TobyGoodwin    |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
  https://github.com/TobyGoodwin     |
  /odd-ghc-pattern-bug               |
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 With some types built by persistent-template, I'm running into very odd
 behaviour. Attempting to pull apart a tuple in one go...

 {{{#!hs
 let (Entity museKey muse, Entity msgKey msg, Entity fldrKey fldr) =
 cluster
 }}}

 fails (or rather, attempting to use msg or fldr fails) with errors like

 {{{
     Couldn't match expected type ‘Folder’ with actual type ‘Folder’
 }}}

 But splitting the pattern up:
 {{{#!hs
   let (a, b, c) = cluster
       Entity museKey muse = a
       Entity msgKey msg = b
       Entity fldrKey fldr = c
 }}}
 everything works normally

 Complete test case here: https://github.com/TobyGoodwin/odd-ghc-pattern-
 bug

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11700>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler