[GHC] #16013: :kind! accepts unsaturated type aliases

[GHC]

#16013: :kind! accepts unsaturated type aliases
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        Reporter:  dmwit             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.3
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dmwit):

 Okay, so further thinking, I'd like to retract part of the complaint. I
 believe I understand why it decides on kind `*`, and agree that's a
 sensible answer. (Namely: I thought in my head `Id :: k -> k`, but the
 compiler chose `Id :: k -> *`, following exactly the rules set out in the
 documentation, so the compiler was right and I was wrong. And I thought in
 my head `Id a = a` matches all types so `Id Foo` should reduce to `Foo` if
 it works at all, but the compiler thought `Id a = a` only matches when `a
 :: *`, so `Id Foo` is a stuck term not one that can reduce, and again the
 compiler was right and I was wrong.)

 But I still think it should probably complain about applying a type family
 or type alias to an unsaturated type alias.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16013#comment:1>
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