[GHC] #9590: AMP breaks `haskell2010` package

[GHC]

#9590: AMP breaks `haskell2010` package
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              Reporter:  hvr         |            Owner:  ekmett
                  Type:  bug         |           Status:  new
              Priority:  high        |        Milestone:  7.10.1
             Component:  Core        |          Version:  7.9
  Libraries                          |         Keywords:  AMP
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:  GHC         |  Related Tickets:
  rejects valid program              |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by hvr):

 Replying to [comment:9 singpolyma]:

 > Isn't this already needed for RebindableSyntax?  Is this not a special
 case of that, or it more different than I think?

 Here's some sketchy idea I also wrote in a reddit comment about an
 hypothetical `RebindableSyntax`-variant called `ExportedRebindedSyntax`
 (modulo bikeshed):

  - Code using a non-default Prelude (like e.g. `haskell2010` or
 `haskell98`) shall just need to hide the `base` package and bring
 `haskell2010` into scope

  - Particularly, code importing that non-default Prelude shall not need to
 enable any language extensions

  - The non-default Prelude module would rebind all syntax elements like
 with `RebindableSyntax`, but it would only export the desugaring rules,
 but does not need to export the symbols such as `IfThenElse` the
 desugaring rules are bound to for client code to work

  - If a module `X` directly or indirectly imports a Prelude module using
 the `ExportedRebindedSyntax` extension, it inherits the desugaring rules,
 and exports them to other modules that import that module `X`. It would be
 illegal to have conflicting desugaring rules brought into scope (c.f.
 conflicting typeclass instances being an error)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9590#comment:10>
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