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, 4 insertions, 4 deletions

diff --git a/compiler/GHC/SysTools/ExtraObj.hs b/compiler/GHC/SysTools/ExtraObj.hs
index 652d8cd897..e8715d4048 100644
--- a/compiler/GHC/SysTools/ExtraObj.hs
+++ b/compiler/GHC/SysTools/ExtraObj.hs
@@ -55,7 +55,7 @@ mkExtraObj dflags extn xs
       -- set of include directories and PIC flags.
       cOpts = map Option (picCCOpts dflags)
                     ++ map (FileOption "-I")
-                            (unitIncludeDirs $ getPackageDetails dflags rtsUnitId)
+                            (unitIncludeDirs $ unsafeGetUnitInfo dflags rtsUnitId)
 
       -- When compiling assembler code, we drop the usual C options, and if the
       -- compiler is Clang, we add an extra argument to tell Clang to ignore
@@ -139,7 +139,7 @@ mkExtraObjToLinkIntoBinary dflags = do
 -- this was included as inline assembly in the main.c file but this
 -- is pretty fragile. gas gets upset trying to calculate relative offsets
 -- that span the .note section (notably .text) when debug info is present
-mkNoteObjsToLinkIntoBinary :: DynFlags -> [InstalledUnitId] -> IO [FilePath]
+mkNoteObjsToLinkIntoBinary :: DynFlags -> [UnitId] -> IO [FilePath]
 mkNoteObjsToLinkIntoBinary dflags dep_packages = do
    link_info <- getLinkInfo dflags dep_packages
 
@@ -166,7 +166,7 @@ mkNoteObjsToLinkIntoBinary dflags dep_packages = do
 -- | Return the "link info" string
 --
 -- See Note [LinkInfo section]
-getLinkInfo :: DynFlags -> [InstalledUnitId] -> IO String
+getLinkInfo :: DynFlags -> [UnitId] -> IO String
 getLinkInfo dflags dep_packages = do
    package_link_opts <- getPackageLinkOpts dflags dep_packages
    pkg_frameworks <- if platformUsesFrameworks (targetPlatform dflags)
@@ -200,7 +200,7 @@ ghcLinkInfoNoteName = "GHC link info"
 
 -- Returns 'False' if it was, and we can avoid linking, because the
 -- previous binary was linked with "the same options".
-checkLinkInfo :: DynFlags -> [InstalledUnitId] -> FilePath -> IO Bool
+checkLinkInfo :: DynFlags -> [UnitId] -> FilePath -> IO Bool
 checkLinkInfo dflags pkg_deps exe_file
  | not (platformSupportsSavingLinkOpts (platformOS (targetPlatform dflags)))
  -- ToDo: Windows and OS X do not use the ELF binary format, so