[GHC] #11598: Cache coercion kinds and roles

[GHC]

#11598: Cache coercion kinds and roles
-------------------------------------+-------------------------------------
        Reporter:  goldfire          |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #8095             |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Description changed by simonpj:

@@ -13,0 +13,4 @@
+
+ This would make #8095 much easier.
+
+ See also #11735.

New description:

 Because we never inspect the structure of a coercion, it is easy to cache
 coercions' kinds and role at the top level, using something like this:

 {{{
 data Coercion = MkCoercion { coercionKind :: Pair Type
                            , coercionRole :: Role
                            , coercionRep  :: CoercionRep }
 data CoercionRep = -- the long, recursive datatype we have now
 }}}

 In the process, various role and type information currently stored in the
 recursive structure could be dropped.

 This would make #8095 much easier.

 See also #11735.

--

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11598#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler