[GHC] #14164: GHC hangs on type family dependency

[GHC]

#14164: GHC hangs on type family dependency
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  merge
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:
                                     |  InjectiveFamilies
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:  indexed-
                                     |  types/should_compile/T14164
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 Assuming the substitution and type t are both well-kinded, yes.

 And I agree with your next sentence. But I'd like to divorce the invariant
 from the type t, because we can. I believe your sentence is implied by

 (*) INVARIANT: If S is a substitution, then inscope(S)\dom(S) is closed
 over kinds.

 This is something easy enough to check for.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14164#comment:13>
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