[GHC] #12653: reexported-modules sometimes gets mangled, causes problems for bootstrap

[GHC]

#12653: reexported-modules sometimes gets mangled, causes problems for bootstrap
-------------------------------------+-------------------------------------
           Reporter:  ezyang         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  highest        |         Milestone:  8.0.2
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 There is a pretty bad bug in Cabal 1.24's support for reexported modules
 (https://github.com/haskell/cabal/pull/3906) which means that, under some
 circumstances, Cabal library will output `reexported-modules` in a form
 that ghc-pkg will misinterpret. The particular instance I've seen is GHC's
 build system incorrectly concluding that GHC.Lexeme is provided by ghc-
 boot rather than ghc-boot-th (because the reexport wasn't parsed
 correctly).

 It does not actually seem possible to work around this given a GHC 8.0.1
 bootstrap, because we need to register ghc-boot using the bootstrapping
 ghc-pkg, which will output the package configuration in mangled form. So
 my advice is:

 1. Fix this bug for GHC 8.0.2, so that at least 8.0.2 bootstrap will work
 even if we have reexported modules in the bootstrap libraries

 2. Stop using reexports in ghc-boot; they're not being used for any good
 reason and will help avoid the bug.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12653>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler