[GHC] #13795: :kind! is not expanding type synonyms anymore

[GHC]

#13795: :kind! is not expanding type synonyms anymore
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        Reporter:  Hjulle            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHCi              |              Version:  8.0.2
      Resolution:                    |             Keywords:  newcomer
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 simonpj):

 We could offer some way to get

 * No processing of the type (currently `:kind`)
 * Type families evaluated (currently `:kind!`)
 * Type families evaluated and type synonyms expanded (`:kind!!` perhaps?)

 And, I suppose, the fourth possibility (expand type synonyms but do not
 evaluate type families).

 But that's probably over-complicated -- few users would care.

 If we are going to have only two possibilities (`:k` and `:k!`), what the
 user manual says makes most sense: `:kind!` evaluates everything, type
 families, type synonyms and all.

 I suppose we could have a `:set -XNoExpandSynonymsOnBang` flag or
 something.

 Implementation is easy.  The hard thing to know is what users want.
 Users, speak up!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13795#comment:6>
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