[GHC] #10266: Split base for Backpack

[GHC]

#10266: Split base for Backpack
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              Reporter:  ezyang      |             Owner:  ezyang
                  Type:  task        |            Status:  new
              Priority:  normal      |         Milestone:
             Component:              |           Version:  7.11
  libraries/base                     |  Operating System:  Unknown/Multiple
              Keywords:  backpack    |   Type of failure:  None/Unknown
          Architecture:              |        Blocked By:
  Unknown/Multiple                   |   Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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 Let's resurrect #1338 and #1580. Our new concrete goal is to have users be
 able to replace 'base' with 'base-sig', which is some signature
 representing the modules from 'base' which we depend on.  Since 'base' is
 a big, complicated package, the ability to specify subsets of 'base' is
 very useful: it can be used to define things like Haskell'98 base, base
 without any unsafe operations, etc.

 Right now, all wired in things live in ghc-prim (I believe). This is good,
 since we can't reasonably abstract wired in things away with a signature:
 GHC will always put them in some well-known place.  However, this is not
 enough: there are many known-key/Rdr things the compiler knows about too,
 which need to be placed in specific package + module locations for GHC to
 be able to reference them; e.g. when deriving instances, etc.

 At the moment, most of these identifiers live in 'base', which is no good.
 So, here's the proposal: all non-rebindable GHC-known identifiers (as per
 PrelNames) should be moved to ghc-prim (or perhaps a new package? I don't
 really care either way) and reexported from the old packages which they
 were available from base. I'll try to work out in detail what moves, how
 to avoid orphan instances, etc.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10266>
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