Re: [GHC] #11078: Access to module renaming with reifyModule, in TemplateHaskell

17 Nov 2015

      #11078: Access to module renaming with reifyModule, in TemplateHaskell
-------------------------------------+-------------------------------------
        Reporter:  cipher1024        |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Template Haskell  |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by jstolarek):

 I just had a quick look at the code. Let's assume we are using definition
 proposed by Richard (slightly modified by me):

 {{{#!hs
 data ImportType = Qualified | Unqualified
   deriving( Show, Eq, Ord, Data, Typeable, Generic )

 data ModuleImport = ModuleImport Module         -- ^ Imported module
                                  ImportType     -- ^ qualified?
                                  (Maybe String) -- ^ synonym
                                  [Name]         -- ^ imported names
                     deriving( Show, Eq, Ord, Data, Typeable, Generic )
 }}}

 I understand that the place where we need to fill in these fields is
 `TcSplice.reifyModule`. At least that is the place where the build fails
 for me after I make changes to TH syntax.

 In `TcM` we have access to `getImports`, which gives us a list of
 `Module`s, each with an assigned `ImportedModsVal`:

 {{{#!hs
 type ImportedMods = ModuleEnv [ImportedModsVal]
 data ImportedModsVal
  = ImportedModsVal {
         imv_name :: ModuleName,         -- ^ The name the module is
 imported with
         imv_span :: SrcSpan,            -- ^ the source span of the whole
 import
         imv_is_safe :: IsSafeImport,    -- ^ whether this is a safe import
         imv_is_hiding :: Bool,          -- ^ whether this is an "hiding"
 import
         imv_all_exports :: GlobalRdrEnv -- ^ all the things the module
 could provide
         }
 }}}

 Now, in `reifyModule` we need the following:

 1. `Module`: this is readily available and created by the existing
 implementation (see `TcSplice.modToTHMod`.
 2. `ImportType`: I can't figure out how we could acces that one
 3. `Maybe String`, aka the module synonym. I would look at `imv_name` to
 see what exactlt it holds. Also, I would adjust TH representation to work
 nicely with information stored in that field.
 4. `[Name]` - it seems that this can be extracted from `imv_all_exports`.

 Does that allow to make progress?

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11078#comment:12
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler