Add HomeUnit type

Since Backpack the "home unit" is much more involved than what it was
before (just an identifier obtained with `-this-unit-id`). Now it is
used in conjunction with `-component-id` and `-instantiated-with` to
configure module instantiations and to detect if we are type-checking an
indefinite unit or compiling a definite one.

This patch introduces a new HomeUnit datatype which is much easier to
understand. Moreover to make GHC support several packages in the same
instances, we will need to handle several HomeUnits so having a
dedicated (documented) type is helpful.

Finally in #14335 we will also need to handle the case where we have no
HomeUnit at all because we are only loading existing interfaces for
plugins which live in a different space compared to units used to
produce target code. Several functions will have to be refactored to
accept "Maybe HomeUnit" parameters instead of implicitly querying the
HomeUnit fields in DynFlags. Having a dedicated type will make this
easier.

Bump haddock submodule

1 files changed, 27 insertions, 22 deletions

diff --git a/compiler/GHC/Iface/Load.hs b/compiler/GHC/Iface/Load.hs
index b7ed66734e..508a6b8281 100644
--- a/compiler/GHC/Iface/Load.hs
+++ b/compiler/GHC/Iface/Load.hs
@@ -82,6 +82,7 @@ import GHC.Types.FieldLabel
 import GHC.Iface.Rename
 import GHC.Types.Unique.DSet
 import GHC.Driver.Plugins
+import GHC.Unit.Home
 
 import Control.Monad
 import Control.Exception
@@ -402,8 +403,9 @@ loadInterface doc_str mod from
   | isHoleModule mod
   -- Hole modules get special treatment
   = do dflags <- getDynFlags
+       let home_unit = mkHomeUnitFromFlags dflags
        -- Redo search for our local hole module
-       loadInterface doc_str (mkHomeModule dflags (moduleName mod)) from
+       loadInterface doc_str (mkHomeModule home_unit (moduleName mod)) from
   | otherwise
   = withTimingSilentD (text "loading interface") (pure ()) $
     do  {       -- Read the state
@@ -414,6 +416,7 @@ loadInterface doc_str mod from
 
                 -- Check whether we have the interface already
         ; dflags <- getDynFlags
+        ; let home_unit = mkHomeUnitFromFlags dflags
         ; case lookupIfaceByModule hpt (eps_PIT eps) mod of {
             Just iface
                 -> return (Succeeded iface) ;   -- Already loaded
@@ -423,7 +426,7 @@ loadInterface doc_str mod from
             _ -> do {
 
         -- READ THE MODULE IN
-        ; read_result <- case (wantHiBootFile dflags eps mod from) of
+        ; read_result <- case (wantHiBootFile home_unit eps mod from) of
                            Failed err             -> return (Failed err)
                            Succeeded hi_boot_file -> computeInterface doc_str hi_boot_file mod
         ; case read_result of {
@@ -494,7 +497,7 @@ loadInterface doc_str mod from
 
         ; WARN( bad_boot, ppr mod )
           updateEps_  $ \ eps ->
-           if elemModuleEnv mod (eps_PIT eps) || is_external_sig dflags iface
+           if elemModuleEnv mod (eps_PIT eps) || is_external_sig home_unit iface
                 then eps
            else if bad_boot
                 -- See Note [Loading your own hi-boot file]
@@ -616,12 +619,12 @@ dontLeakTheHPT thing_inside = do
 -- | Returns @True@ if a 'ModIface' comes from an external package.
 -- In this case, we should NOT load it into the EPS; the entities
 -- should instead come from the local merged signature interface.
-is_external_sig :: DynFlags -> ModIface -> Bool
-is_external_sig dflags iface =
+is_external_sig :: HomeUnit -> ModIface -> Bool
+is_external_sig home_unit iface =
     -- It's a signature iface...
     mi_semantic_module iface /= mi_module iface &&
     -- and it's not from the local package
-    moduleUnit (mi_module iface) /= homeUnit dflags
+    not (isHomeModule home_unit (mi_module iface))
 
 -- | This is an improved version of 'findAndReadIface' which can also
 -- handle the case when a user requests @p[A=<B>]:M@ but we only
@@ -643,8 +646,9 @@ computeInterface ::
 computeInterface doc_str hi_boot_file mod0 = do
     MASSERT( not (isHoleModule mod0) )
     dflags <- getDynFlags
+    let home_unit = mkHomeUnitFromFlags dflags
     case getModuleInstantiation mod0 of
-        (imod, Just indef) | homeUnitIsIndefinite dflags -> do
+        (imod, Just indef) | isHomeUnitIndefinite home_unit -> do
             r <- findAndReadIface doc_str imod mod0 hi_boot_file
             case r of
                 Succeeded (iface0, path) -> do
@@ -702,13 +706,13 @@ moduleFreeHolesPrecise doc_str mod
                 return (Succeeded (renameFreeHoles ifhs insts))
             Failed err -> return (Failed err)
 
-wantHiBootFile :: DynFlags -> ExternalPackageState -> Module -> WhereFrom
+wantHiBootFile :: HomeUnit -> ExternalPackageState -> Module -> WhereFrom
                -> MaybeErr MsgDoc IsBootInterface
 -- Figure out whether we want Foo.hi or Foo.hi-boot
-wantHiBootFile dflags eps mod from
+wantHiBootFile home_unit eps mod from
   = case from of
        ImportByUser usr_boot
-          | usr_boot == IsBoot && not this_package
+          | usr_boot == IsBoot && notHomeModule home_unit mod
           -> Failed (badSourceImport mod)
           | otherwise -> Succeeded usr_boot
 
@@ -716,10 +720,12 @@ wantHiBootFile dflags eps mod from
           -> Succeeded NotBoot
 
        ImportBySystem
-          | not this_package   -- If the module to be imported is not from this package
-          -> Succeeded NotBoot -- don't look it up in eps_is_boot, because that is keyed
-                               -- on the ModuleName of *home-package* modules only.
-                               -- We never import boot modules from other packages!
+          | notHomeModule home_unit mod
+          -> Succeeded NotBoot
+             -- If the module to be imported is not from this package
+             -- don't look it up in eps_is_boot, because that is keyed
+             -- on the ModuleName of *home-package* modules only.
+             -- We never import boot modules from other packages!
 
           | otherwise
           -> case lookupUFM (eps_is_boot eps) (moduleName mod) of
@@ -729,8 +735,6 @@ wantHiBootFile dflags eps mod from
                   Succeeded NotBoot
                      -- The boot-ness of the requested interface,
                      -- based on the dependencies in directly-imported modules
-  where
-    this_package = homeUnit dflags == moduleUnit mod
 
 badSourceImport :: Module -> SDoc
 badSourceImport mod
@@ -922,6 +926,7 @@ findAndReadIface doc_str mod wanted_mod_with_insts hi_boot_file
                -- Look for the file
                hsc_env <- getTopEnv
                mb_found <- liftIO (findExactModule hsc_env mod)
+               let home_unit = mkHomeUnitFromFlags dflags
                case mb_found of
                    InstalledFound loc mod -> do
                        -- Found file, so read it
@@ -929,7 +934,7 @@ findAndReadIface doc_str mod wanted_mod_with_insts hi_boot_file
                                                            (ml_hi_file loc)
 
                        -- See Note [Home module load error]
-                       if moduleUnit mod `unitIdEq` homeUnit dflags &&
+                       if isHomeInstalledModule home_unit mod &&
                           not (isOneShot (ghcMode dflags))
                            then return (Failed (homeModError mod loc))
                            else do r <- read_file file_path
@@ -1020,8 +1025,8 @@ readIface wanted_mod file_path
 *********************************************************
 -}
 
-initExternalPackageState :: DynFlags -> ExternalPackageState
-initExternalPackageState dflags
+initExternalPackageState :: HomeUnit -> ExternalPackageState
+initExternalPackageState home_unit
   = EPS {
       eps_is_boot          = emptyUFM,
       eps_PIT              = emptyPackageIfaceTable,
@@ -1041,9 +1046,9 @@ initExternalPackageState dflags
     }
     where
       enableBignumRules
-         | homeUnitId dflags == primUnitId   = EnableBignumRules False
-         | homeUnitId dflags == bignumUnitId = EnableBignumRules False
-         | otherwise                         = EnableBignumRules True
+         | isHomeUnitInstanceOf home_unit primUnitId   = EnableBignumRules False
+         | isHomeUnitInstanceOf home_unit bignumUnitId = EnableBignumRules False
+         | otherwise                                   = EnableBignumRules True
       builtinRules' = builtinRules enableBignumRules
 
 {-