[GHC] #10279: panic on haskell-src-exts

[GHC]

#10279: panic on haskell-src-exts
-------------------------------------+-------------------------------------
        Reporter:  throwaway123      |                   Owner:  ezyang
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Linux             |            Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash                              |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by simonpj):

 Te basic problem here, which also happened in #, is that `"haskell-src-
 exts-1.16.0.1"` is not the '''key''' of any package; it's the
 '''name/version''' of the package.  Reminder
  * The name/version of a package is something like `haskell-src-
 exts-1.16.0.1`.  It represents the source code of a particular released
 package.
  * The key of a package is something like `haske_7Ftlz85Zj6I3uisdzq1Sbd`;
 it represents a compiled instance of the package.

 Global names (built with `NameG`) contain package keys.

 Edward Y and I talked. Here's our proposal.

 1. Add a new function
 {{{
 reifyPackage :: String   -- Package name
              -> String   -- Version
              -> Q [Package]
 }}}
   which, given a package name/version returns all the installed packages
 with that name and version.

   The auxiliary types are
 {{{
 data Package = Pkg PkgKey        -- Abstract; may grow more fields
 newtype PkgKey = PkgKey String   -- Abstract;

 packageKey :: Package -> PkgKey  -- Accessor
 packageKey (Pkg p) = p

 mkPackageKey :: String -> PkgKey
 mkPackageKey = PkgKey   -- Use with caution; these strings are not easy to
 come up with
                         -- eg "haske_7Ftlz85Zj6I3uisdzq1Sbd"
 }}}

  2. Improve the error message when splicing code that mentions a bad
 `PkgKey` in a `NameG`, as in comment:8

 Notes

  * A TH `NameG` currently contains a `PkgName`, defined thus:
 {{{
 newtype PkgName = PkgName String        -- package name
 }}}
   This is badly misleading; we propose to rename it to `PkgKey`, defined
 above.  You can get a `PkgKey` from `reifyPackage` plus `packageKey`; or
 in some other out-of-band-way plus `mkPkgKey`.

   * `reifyPackage` returns a list of `Packages`.  There can be more than
 one if the sane package name/version is installed wrt different
 dependencies; but this is atypical.   At some point we may need to support
 bigger API for `Package`, which lets you get its dependencies.

 See also #10330.

 None of this is for 7.10; it's a proposal for 7.12.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10279#comment:10>
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