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, 14 insertions, 14 deletions

diff --git a/compiler/GHC/Iface/Load.hs b/compiler/GHC/Iface/Load.hs
index 0068441ee3..c35a426e07 100644
--- a/compiler/GHC/Iface/Load.hs
+++ b/compiler/GHC/Iface/Load.hs
@@ -619,7 +619,7 @@ is_external_sig dflags iface =
     -- It's a signature iface...
     mi_semantic_module iface /= mi_module iface &&
     -- and it's not from the local package
-    moduleUnitId (mi_module iface) /= thisPackage dflags
+    moduleUnit (mi_module iface) /= thisPackage dflags
 
 -- | This is an improved version of 'findAndReadIface' which can also
 -- handle the case when a user requests @p[A=<B>]:M@ but we only
@@ -641,14 +641,14 @@ computeInterface ::
 computeInterface doc_str hi_boot_file mod0 = do
     MASSERT( not (isHoleModule mod0) )
     dflags <- getDynFlags
-    case splitModuleInsts mod0 of
-        (imod, Just indef) | not (unitIdIsDefinite (thisPackage dflags)) -> do
+    case getModuleInstantiation mod0 of
+        (imod, Just indef) | not (unitIsDefinite (thisPackage dflags)) -> do
             r <- findAndReadIface doc_str imod mod0 hi_boot_file
             case r of
                 Succeeded (iface0, path) -> do
                     hsc_env <- getTopEnv
                     r <- liftIO $
-                        rnModIface hsc_env (indefUnitIdInsts (indefModuleUnitId indef))
+                        rnModIface hsc_env (instUnitInsts (moduleUnit indef))
                                    Nothing iface0
                     case r of
                         Right x -> return (Succeeded (x, path))
@@ -672,9 +672,9 @@ moduleFreeHolesPrecise
 moduleFreeHolesPrecise doc_str mod
  | moduleIsDefinite mod = return (Succeeded emptyUniqDSet)
  | otherwise =
-   case splitModuleInsts mod of
+   case getModuleInstantiation mod of
     (imod, Just indef) -> do
-        let insts = indefUnitIdInsts (indefModuleUnitId indef)
+        let insts = instUnitInsts (moduleUnit indef)
         traceIf (text "Considering whether to load" <+> ppr mod <+>
                  text "to compute precise free module holes")
         (eps, hpt) <- getEpsAndHpt
@@ -726,13 +726,13 @@ wantHiBootFile dflags eps mod from
                      -- The boot-ness of the requested interface,
                      -- based on the dependencies in directly-imported modules
   where
-    this_package = thisPackage dflags == moduleUnitId mod
+    this_package = thisPackage dflags == moduleUnit mod
 
 badSourceImport :: Module -> SDoc
 badSourceImport mod
   = hang (text "You cannot {-# SOURCE #-} import a module from another package")
        2 (text "but" <+> quotes (ppr mod) <+> ptext (sLit "is from package")
-          <+> quotes (ppr (moduleUnitId mod)))
+          <+> quotes (ppr (moduleUnit mod)))
 
 -----------------------------------------------------
 --      Loading type/class/value decls
@@ -925,7 +925,7 @@ findAndReadIface doc_str mod wanted_mod_with_insts hi_boot_file
                                                            (ml_hi_file loc)
 
                        -- See Note [Home module load error]
-                       if installedModuleUnitId mod `installedUnitIdEq` thisPackage dflags &&
+                       if moduleUnit mod `unitIdEq` thisPackage dflags &&
                           not (isOneShot (ghcMode dflags))
                            then return (Failed (homeModError mod loc))
                            else do r <- read_file file_path
@@ -935,7 +935,7 @@ findAndReadIface doc_str mod wanted_mod_with_insts hi_boot_file
                        traceIf (text "...not found")
                        dflags <- getDynFlags
                        return (Failed (cannotFindInterface dflags
-                                           (installedModuleName mod) err))
+                                           (moduleName mod) err))
     where read_file file_path = do
               traceIf (text "readIFace" <+> text file_path)
               -- Figure out what is recorded in mi_module.  If this is
@@ -943,11 +943,11 @@ findAndReadIface doc_str mod wanted_mod_with_insts hi_boot_file
               -- if it's indefinite, the inside will be uninstantiated!
               dflags <- getDynFlags
               let wanted_mod =
-                    case splitModuleInsts wanted_mod_with_insts of
+                    case getModuleInstantiation wanted_mod_with_insts of
                         (_, Nothing) -> wanted_mod_with_insts
                         (_, Just indef_mod) ->
-                          indefModuleToModule dflags
-                            (generalizeIndefModule indef_mod)
+                          instModuleToModule (pkgState dflags)
+                            (uninstantiateInstantiatedModule indef_mod)
               read_result <- readIface wanted_mod file_path
               case read_result of
                 Failed err -> return (Failed (badIfaceFile file_path err))
@@ -1272,7 +1272,7 @@ badIfaceFile file err
 
 hiModuleNameMismatchWarn :: DynFlags -> Module -> Module -> MsgDoc
 hiModuleNameMismatchWarn dflags requested_mod read_mod
- | moduleUnitId requested_mod == moduleUnitId read_mod =
+ | moduleUnit requested_mod == moduleUnit read_mod =
     sep [text "Interface file contains module" <+> quotes (ppr read_mod) <> comma,
          text "but we were expecting module" <+> quotes (ppr requested_mod),
          sep [text "Probable cause: the source code which generated interface file",