[GHC] #12442: Pure unifier usually doesn't need to unify kinds

[GHC]

#12442: Pure unifier usually doesn't need to unify kinds
-------------------------------------+-------------------------------------
        Reporter:  goldfire          |                Owner:  goldfire
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:  fixed             |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  dependent/should_compile/T12442
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2433
       Wiki Page:                    |
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Changes (by alpmestan):

 * cc: alpmestan (added)


Comment:

 I ran `./validate --slow` yesterday and `T12442` is failing in all test
 ways:

 {{{
    /tmp/ghctest-kabnnx7e/test
 spaces/./dependent/should_compile/T12442.run
 T12442 [exit code non-0] (normal)
    /tmp/ghctest-kabnnx7e/test
 spaces/./dependent/should_compile/T12442.run
 T12442 [exit code non-0] (hpc)
    /tmp/ghctest-kabnnx7e/test
 spaces/./dependent/should_compile/T12442.run
 T12442 [exit code non-0] (optasm)
    /tmp/ghctest-kabnnx7e/test
 spaces/./dependent/should_compile/T12442.run
 T12442 [exit code non-0] (profasm)
    /tmp/ghctest-kabnnx7e/test
 spaces/./dependent/should_compile/T12442.run
 T12442 [exit code non-0] (optllvm)
 }}}

 Always with the same panic:

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.5.20180329 for x86_64-unknown-linux):
         ASSERT failed! file compiler/typecheck/TcTyClsDecls.hs, line 1531
 }}}

 This sounds like an actual problem, but if you don't mind I'll leave it to
 you Richard & Simon to decide/figure out whether this ticket should be re-
 opened or whether this is a new, unrelated problem that deserves its own
 ticket.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12442#comment:10>
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