Refactoring unit management code

Over the years the unit management code has been modified a lot to keep
up with changes in Cabal (e.g. support for several library components in
the same package), to integrate BackPack, etc. I found it very hard to
understand as the terminology wasn't consistent, was referring to past
concepts, etc.

The terminology is now explained as clearly as I could in the Note
"About Units" and the code is refactored to reflect it.

-------------------

Many names were misleading: UnitId is not an Id but could be a virtual
unit (an indefinite one instantiated on the fly), IndefUnitId
constructor may contain a definite instantiated unit, etc.

   * Rename IndefUnitId into InstantiatedUnit
   * Rename IndefModule into InstantiatedModule
   * Rename UnitId type into Unit
   * Rename IndefiniteUnitId constructor into VirtUnit
   * Rename DefiniteUnitId constructor into RealUnit
   * Rename packageConfigId into mkUnit
   * Rename getPackageDetails into unsafeGetUnitInfo
   * Rename InstalledUnitId into UnitId

Remove references to misleading ComponentId: a ComponentId is just an
indefinite unit-id to be instantiated.

   * Rename ComponentId into IndefUnitId
   * Rename ComponentDetails into UnitPprInfo
   * Fix display of UnitPprInfo with empty version: this is now used for
     units dynamically generated by BackPack

Generalize several types (Module, Unit, etc.) so that they can be used
with different unit identifier types: UnitKey, UnitId, Unit, etc.

   * GenModule: Module, InstantiatedModule and InstalledModule are now
     instances of this type
   * Generalize DefUnitId, IndefUnitId, Unit, InstantiatedUnit,
     PackageDatabase

Replace BackPack fake "hole" UnitId by a proper HoleUnit constructor.

Add basic support for UnitKey. They should be used more in the future to
avoid mixing them up with UnitId as we do now.

Add many comments.

Update Haddock submodule

1 files changed, 5 insertions, 5 deletions

diff --git a/compiler/GHC/Driver/CodeOutput.hs b/compiler/GHC/Driver/CodeOutput.hs
index cba5d1b644..446deb2c99 100644
--- a/compiler/GHC/Driver/CodeOutput.hs
+++ b/compiler/GHC/Driver/CodeOutput.hs
@@ -60,7 +60,7 @@ codeOutput :: DynFlags
            -> ForeignStubs
            -> [(ForeignSrcLang, FilePath)]
            -- ^ additional files to be compiled with with the C compiler
-           -> [InstalledUnitId]
+           -> [UnitId]
            -> Stream IO RawCmmGroup a                       -- Compiled C--
            -> IO (FilePath,
                   (Bool{-stub_h_exists-}, Maybe FilePath{-stub_c_exists-}),
@@ -120,7 +120,7 @@ doOutput filenm io_action = bracket (openFile filenm WriteMode) hClose io_action
 outputC :: DynFlags
         -> FilePath
         -> Stream IO RawCmmGroup a
-        -> [InstalledUnitId]
+        -> [UnitId]
         -> IO a
 
 outputC dflags filenm cmm_stream packages
@@ -133,7 +133,7 @@ outputC dflags filenm cmm_stream packages
          --   * -#include options from the cmdline and OPTIONS pragmas
          --   * the _stub.h file, if there is one.
          --
-         let rts = getPackageDetails dflags rtsUnitId
+         let rts = unsafeGetUnitInfo dflags rtsUnitId
 
          let cc_injects = unlines (map mk_include (unitIncludes rts))
              mk_include h_file =
@@ -142,7 +142,7 @@ outputC dflags filenm cmm_stream packages
                  '<':_      -> "#include "++h_file
                  _          -> "#include \""++h_file++"\""
 
-         let pkg_names = map installedUnitIdString packages
+         let pkg_names = map unitIdString packages
 
          doOutput filenm $ \ h -> do
             hPutStr h ("/* GHC_PACKAGES " ++ unwords pkg_names ++ "\n*/\n")
@@ -225,7 +225,7 @@ outputForeignStubs dflags mod location stubs
 
         -- we need the #includes from the rts package for the stub files
         let rts_includes =
-               let rts_pkg = getPackageDetails dflags rtsUnitId in
+               let rts_pkg = unsafeGetUnitInfo dflags rtsUnitId in
                concatMap mk_include (unitIncludes rts_pkg)
             mk_include i = "#include \"" ++ i ++ "\"\n"