Re: [GHC] #14991: GHC HEAD regression involving TYPEs in type families

2 Apr 2018

      #14991: GHC HEAD regression involving TYPEs in type families
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        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.5
  checker)                           |             Keywords:  TypeInType,
      Resolution:                    |  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Richard Eisenberg ):

 In [changeset:"d8d4266bf73790f65b223ec16f645763eaed8be3/ghc"
 d8d4266b/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="d8d4266bf73790f65b223ec16f645763eaed8be3"
 Fix #14991.

 It turns out that solveEqualities really does need to use simpl_top.
 I thought that solveWanteds would be enough, and no existing test
 case showed up the different. #14991 shows that we need simpl_top.
 Easy enough to fix.

 test case: dependent/should_compile/T14991
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14991#comment:6
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