[GHC] #7730: :info and polykinds

[GHC]

#7730: :info and polykinds
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        Reporter:  monoidal                 |            Owner:  archblob
            Type:  bug                      |           Status:  new
        Priority:  normal                   |        Milestone:  7.10.1
       Component:  Compiler (Type checker)  |          Version:  7.6.2
      Resolution:                           |         Keywords:
Operating System:  Unknown/Multiple         |     Architecture:
 Type of failure:  None/Unknown             |  Unknown/Multiple
       Test Case:                           |       Difficulty:  Unknown
        Blocking:                           |       Blocked By:
                                            |  Related Tickets:  #8776
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Comment (by simonpj):

 Some responses

  * On the `IfaceTcArg` thing (comment 35), I suggested a whole new list
 type because it'll be more compact and faster to parse in interface files.
 Rather than two bytes and two decisions (nil/cons, and type/kind) there'll
 just be one.  But the data type would need a Note to explain that
 reasoning.

  * On the qualified names point (also comment 35), I can see that
 `IfaceDecl`s only have an `OccName` in them because interface declarations
 "know" their host module. That's no longer true when converting arbitrary
 `TyThings` to `IfaceSyn`. So the `ifName` field of `IfaceDecl` will have
 to become `IfExtName`.  Probably not too bad.

  * Re promotion (comment 36), yes I agree.

 All of these things will make interface files a little more verbose. It
 probably won't have any effect, but could you do some performance checks?
 With these changes alone:
  * Measure the effect on `.hi` file sizes for libraries (eg `base`)
  * Measure the effect on compile times (or, easier to get at, compiler
 allocation), say when bootstrapping GHC, or compiling the base libraries.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7730#comment:37>
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