[GHC] #10701: -fth-dec-file uses qualified names from hidden modules

[GHC]

#10701: -fth-dec-file uses qualified names from hidden modules
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              Reporter:  Fabian      |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.1
              Keywords:  TH          |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 In cross compilation builds, the current TH situation is a bit of a
 showstopper. However, much TH code is 'safe' to cross-compile. Before the
 TH situation is solved, it would be great if GHC could automate as much of
 the work-around process as possible. -dth-dec-file is a big step on the
 way to create a non-TH version of the source. However, there are some
 problems with the generated code. One is that qualified names from hidden
 modules are used. A instance declaration for Aeson.ToJSON is outputted as
 follows:

 {{{#!hs
 instance Data.Aeson.Types.Class.ToJSON InputDropboxFiles where
 }}}

 Ideally, GHC would be able to combine the splice output with the original
 file, replacing all $() with the corresponding splice, and even generate
 correct imports. I personally think this would be a great solution to the
 TH problem. Most cross-compilation projects could just generate the non-TH
 version with the host GHC, and the few that depends on architecture
 specific variables can be edited before cross-compiled

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10701>
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