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/ghc/GHCi/UI.hs b/ghc/GHCi/UI.hs
index 0da9741f30..3006af68c1 100644
--- a/ghc/GHCi/UI.hs
+++ b/ghc/GHCi/UI.hs
@@ -57,7 +57,7 @@ import GHC.Driver.Types ( tyThingParent_maybe, handleFlagWarnings, getSafeMode,
                   hsc_dynLinker, hsc_interp )
 import GHC.Types.Module
 import GHC.Types.Name
-import GHC.Driver.Packages ( unitIsTrusted, getPackageDetails, getInstalledPackageDetails,
+import GHC.Driver.Packages ( unitIsTrusted, unsafeGetUnitInfo, getInstalledPackageDetails,
                              listVisibleModuleNames, pprFlag )
 import GHC.Iface.Syntax ( showToHeader )
 import GHC.Core.Ppr.TyThing
@@ -2340,8 +2340,8 @@ isSafeModule m = do
     mname = GHC.moduleNameString $ GHC.moduleName m
 
     packageTrusted dflags md
-        | thisPackage dflags == moduleUnitId md = True
-        | otherwise = unitIsTrusted $ getPackageDetails dflags (moduleUnitId md)
+        | thisPackage dflags == moduleUnit md = True
+        | otherwise = unitIsTrusted $ unsafeGetUnitInfo dflags (moduleUnit md)
 
     tallyPkgs dflags deps | not (packageTrustOn dflags) = (S.empty, S.empty)
                           | otherwise = S.partition part deps
@@ -4185,7 +4185,7 @@ lookupModuleName :: GHC.GhcMonad m => ModuleName -> m Module
 lookupModuleName mName = GHC.lookupModule mName Nothing
 
 isHomeModule :: Module -> Bool
-isHomeModule m = GHC.moduleUnitId m == mainUnitId
+isHomeModule m = GHC.moduleUnit m == mainUnitId
 
 -- TODO: won't work if home dir is encoded.
 -- (changeDirectory may not work either in that case.)
@@ -4209,7 +4209,7 @@ wantInterpretedModuleName modname = do
    modl <- lookupModuleName modname
    let str = moduleNameString modname
    dflags <- getDynFlags
-   when (GHC.moduleUnitId modl /= thisPackage dflags) $
+   when (GHC.moduleUnit modl /= thisPackage dflags) $
       throwGhcException (CmdLineError ("module '" ++ str ++ "' is from another package;\nthis command requires an interpreted module"))
    is_interpreted <- GHC.moduleIsInterpreted modl
    when (not is_interpreted) $