[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:  new
        Priority:  normal            |            Milestone:  8.6.1
       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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Changes (by simonpj):

 * status:  closed => new
 * resolution:  fixed =>


Comment:

 Richard and I had a chat yesterday.  He is going to

 * Write the invariant in comment:13, along with a Note to explain it
 (based on this ticket).

 * Add an ASSERT to check it.

 * Comment `substTy` and `substCo`, in the variable cases, to explain why
 we do not need to substitute in the kind of a type variable, or the type
 of a coercion variable.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14164#comment:15>
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