1 files changed, 120 insertions, 13 deletions

diff --git a/compiler/GHC/Unit/Module/Graph.hs b/compiler/GHC/Unit/Module/Graph.hs
index faa3ae9b1a..5b5d152711 100644
--- a/compiler/GHC/Unit/Module/Graph.hs
+++ b/compiler/GHC/Unit/Module/Graph.hs
@@ -1,17 +1,26 @@
+{-# LANGUAGE LambdaCase      #-}
 {-# LANGUAGE RecordWildCards #-}
 
 module GHC.Unit.Module.Graph
    ( ModuleGraph
+   , ModuleGraphNode(..)
    , emptyMG
    , mkModuleGraph
+   , mkModuleGraph'
    , extendMG
+   , extendMGInst
+   , extendMG'
+   , filterToposortToModules
    , mapMG
    , mgModSummaries
+   , mgModSummaries'
+   , mgExtendedModSummaries
    , mgElemModule
    , mgLookupModule
    , mgBootModules
    , needsTemplateHaskellOrQQ
    , isTemplateHaskellOrQQNonBoot
+   , showModMsg
    )
 where
 
@@ -19,21 +28,50 @@ import GHC.Prelude
 
 import qualified GHC.LanguageExtensions as LangExt
 
+import GHC.Data.Maybe
+import GHC.Data.Graph.Directed ( SCC(..) )
+
+import GHC.Driver.Backend
+import GHC.Driver.Ppr
 import GHC.Driver.Session
 
+import GHC.Types.SourceFile ( hscSourceString )
+
 import GHC.Unit.Module.ModSummary
 import GHC.Unit.Module.Env
 import GHC.Unit.Types
-
-
--- | A ModuleGraph contains all the nodes from the home package (only).
--- There will be a node for each source module, plus a node for each hi-boot
--- module.
+import GHC.Utils.Outputable
+
+import System.FilePath
+
+-- | A '@ModuleGraphNode@' is a node in the '@ModuleGraph@'.
+-- Edges between nodes mark dependencies arising from module imports
+-- and dependencies arising from backpack instantiations.
+data ModuleGraphNode
+  -- | Instantiation nodes track the instantiation of other units
+  -- (backpack dependencies) with the holes (signatures) of the current package.
+  = InstantiationNode InstantiatedUnit
+  -- | There is a module summary node for each module, signature, and boot module being built.
+  | ModuleNode ExtendedModSummary
+
+instance Outputable ModuleGraphNode where
+  ppr = \case
+    InstantiationNode iuid -> ppr iuid
+    ModuleNode ems -> ppr ems
+
+-- | A '@ModuleGraph@' contains all the nodes from the home package (only). See
+-- '@ModuleGraphNode@' for information about the nodes.
+--
+-- Modules need to be compiled. hs-boots need to be typechecked before
+-- the associated "real" module so modules with {-# SOURCE #-} imports can be
+-- built. Instantiations also need to be typechecked to ensure that the module
+-- fits the signature. Substantiation typechecking is roughly comparable to the
+-- check that the module and its hs-boot agree.
 --
 -- The graph is not necessarily stored in topologically-sorted order.  Use
 -- 'GHC.topSortModuleGraph' and 'GHC.Data.Graph.Directed.flattenSCC' to achieve this.
 data ModuleGraph = ModuleGraph
-  { mg_mss :: [ModSummary]
+  { mg_mss :: [ModuleGraphNode]
   , mg_non_boot :: ModuleEnv ModSummary
     -- a map of all non-boot ModSummaries keyed by Modules
   , mg_boot :: ModuleSet
@@ -56,7 +94,9 @@ needsTemplateHaskellOrQQ mg = mg_needs_th_or_qq mg
 -- To preserve invariants 'f' can't change the isBoot status.
 mapMG :: (ModSummary -> ModSummary) -> ModuleGraph -> ModuleGraph
 mapMG f mg@ModuleGraph{..} = mg
-  { mg_mss = map f mg_mss
+  { mg_mss = flip fmap mg_mss $ \case
+      InstantiationNode iuid -> InstantiationNode iuid
+      ModuleNode (ExtendedModSummary ms bds) -> ModuleNode (ExtendedModSummary (f ms) bds)
   , mg_non_boot = mapModuleEnv f mg_non_boot
   }
 
@@ -64,7 +104,13 @@ mgBootModules :: ModuleGraph -> ModuleSet
 mgBootModules ModuleGraph{..} = mg_boot
 
 mgModSummaries :: ModuleGraph -> [ModSummary]
-mgModSummaries = mg_mss
+mgModSummaries mg = [ m | ModuleNode (ExtendedModSummary m _) <- mgModSummaries' mg ]
+
+mgExtendedModSummaries :: ModuleGraph -> [ExtendedModSummary]
+mgExtendedModSummaries mg = [ ems | ModuleNode ems <- mgModSummaries' mg ]
+
+mgModSummaries' :: ModuleGraph -> [ModuleGraphNode]
+mgModSummaries' = mg_mss
 
 mgElemModule :: ModuleGraph -> Module -> Bool
 mgElemModule ModuleGraph{..} m = elemModuleEnv m mg_non_boot
@@ -82,11 +128,11 @@ isTemplateHaskellOrQQNonBoot ms =
     || xopt LangExt.QuasiQuotes (ms_hspp_opts ms)) &&
   (isBootSummary ms == NotBoot)
 
--- | Add a ModSummary to ModuleGraph. Assumes that the new ModSummary is
+-- | Add an ExtendedModSummary to ModuleGraph. Assumes that the new ModSummary is
 -- not an element of the ModuleGraph.
-extendMG :: ModuleGraph -> ModSummary -> ModuleGraph
-extendMG ModuleGraph{..} ms = ModuleGraph
-  { mg_mss = ms:mg_mss
+extendMG :: ModuleGraph -> ExtendedModSummary -> ModuleGraph
+extendMG ModuleGraph{..} ems@(ExtendedModSummary ms _) = ModuleGraph
+  { mg_mss = ModuleNode ems : mg_mss
   , mg_non_boot = case isBootSummary ms of
       IsBoot -> mg_non_boot
       NotBoot -> extendModuleEnv mg_non_boot (ms_mod ms) ms
@@ -96,6 +142,67 @@ extendMG ModuleGraph{..} ms = ModuleGraph
   , mg_needs_th_or_qq = mg_needs_th_or_qq || isTemplateHaskellOrQQNonBoot ms
   }
 
-mkModuleGraph :: [ModSummary] -> ModuleGraph
+extendMGInst :: ModuleGraph -> InstantiatedUnit -> ModuleGraph
+extendMGInst mg depUnitId = mg
+  { mg_mss = InstantiationNode depUnitId : mg_mss mg
+  }
+
+extendMG' :: ModuleGraph -> ModuleGraphNode -> ModuleGraph
+extendMG' mg = \case
+  InstantiationNode depUnitId -> extendMGInst mg depUnitId
+  ModuleNode ems -> extendMG mg ems
+
+mkModuleGraph :: [ExtendedModSummary] -> ModuleGraph
 mkModuleGraph = foldr (flip extendMG) emptyMG
 
+mkModuleGraph' :: [ModuleGraphNode] -> ModuleGraph
+mkModuleGraph' = foldr (flip extendMG') emptyMG
+
+-- | This function filters out all the instantiation nodes from each SCC of a
+-- topological sort. Use this with care, as the resulting "strongly connected components"
+-- may not really be strongly connected in a direct way, as instantiations have been
+-- removed. It would probably be best to eliminate uses of this function where possible.
+filterToposortToModules
+  :: [SCC ModuleGraphNode] -> [SCC ModSummary]
+filterToposortToModules = mapMaybe $ mapMaybeSCC $ \case
+  InstantiationNode _ -> Nothing
+  ModuleNode (ExtendedModSummary node _) -> Just node
+  where
+    -- This higher order function is somewhat bogus,
+    -- as the definition of "strongly connected component"
+    -- is not necessarily respected.
+    mapMaybeSCC :: (a -> Maybe b) -> SCC a -> Maybe (SCC b)
+    mapMaybeSCC f = \case
+      AcyclicSCC a -> AcyclicSCC <$> f a
+      CyclicSCC as -> case mapMaybe f as of
+        [] -> Nothing
+        [a] -> Just $ AcyclicSCC a
+        as -> Just $ CyclicSCC as
+
+showModMsg :: DynFlags -> Bool -> ModuleGraphNode -> SDoc
+showModMsg _ _ (InstantiationNode indef_unit) =
+  ppr $ instUnitInstanceOf indef_unit
+showModMsg dflags recomp (ModuleNode (ExtendedModSummary mod_summary _)) =
+  if gopt Opt_HideSourcePaths dflags
+      then text mod_str
+      else hsep $
+         [ text (mod_str ++ replicate (max 0 (16 - length mod_str)) ' ')
+         , char '('
+         , text (op $ msHsFilePath mod_summary) <> char ','
+         ] ++
+         if gopt Opt_BuildDynamicToo dflags
+            then [ text obj_file <> char ','
+                 , text dyn_file
+                 , char ')'
+                 ]
+            else [ text obj_file, char ')' ]
+  where
+    op       = normalise
+    mod      = moduleName (ms_mod mod_summary)
+    mod_str  = showPpr dflags mod ++ hscSourceString (ms_hsc_src mod_summary)
+    dyn_file = op $ msDynObjFilePath mod_summary dflags
+    obj_file = case backend dflags of
+                Interpreter | recomp -> "interpreted"
+                NoBackend            -> "nothing"
+                _                    -> (op $ msObjFilePath mod_summary)
+