Automatically detect and split mutually recursive blocks in let expre…

…ssions (#1894)

- Closes #1677

src/Juvix/Compiler/Abstract/Extra/DependencyBuilder.hs

@@ -1,4 +1,4 @@
-module Juvix.Compiler.Abstract.Extra.DependencyBuilder (buildDependencyInfo, ExportsTable) where
+module Juvix.Compiler.Abstract.Extra.DependencyBuilder (buildDependencyInfo, buildDependencyInfoExpr, ExportsTable) where
 
 import Data.HashMap.Strict qualified as HashMap
 import Data.HashSet qualified as HashSet
@@ -18,7 +18,23 @@ type ExportsTable = HashSet NameId
 
 buildDependencyInfo :: NonEmpty TopModule -> ExportsTable -> NameDependencyInfo
 buildDependencyInfo ms tab =
-  createDependencyInfo graph startNodes
+  buildDependencyInfoHelper tab (mapM_ goModule ms)
+
+buildDependencyInfoExpr :: Expression -> NameDependencyInfo
+buildDependencyInfoExpr = buildDependencyInfoHelper mempty . goExpression Nothing
+
+buildDependencyInfoHelper ::
+  ExportsTable ->
+  ( Sem
+      '[ Reader ExportsTable,
+         State DependencyGraph,
+         State StartNodes,
+         State VisitedModules
+       ]
+      ()
+  ) ->
+  NameDependencyInfo
+buildDependencyInfoHelper tbl m = createDependencyInfo graph startNodes
   where
     startNodes :: StartNodes
     graph :: DependencyGraph
@@ -27,12 +43,14 @@ buildDependencyInfo ms tab =
         evalState (HashSet.empty :: VisitedModules) $
           runState HashSet.empty $
             execState HashMap.empty $
-              runReader tab $
-                mapM_ goModule ms
+              runReader tbl m
 
 addStartNode :: (Member (State StartNodes) r) => Name -> Sem r ()
 addStartNode n = modify (HashSet.insert n)
 
+addEdgeMay :: (Member (State DependencyGraph) r) => Maybe Name -> Name -> Sem r ()
+addEdgeMay mn1 n2 = whenJust mn1 $ \n1 -> addEdge n1 n2
+
 addEdge :: (Member (State DependencyGraph) r) => Name -> Name -> Sem r ()
 addEdge n1 n2 =
   modify
@@ -87,16 +105,16 @@ goStatement modName = \case
   StatementAxiom ax -> do
     checkStartNode (ax ^. axiomName)
     addEdge (ax ^. axiomName) modName
-    goExpression (ax ^. axiomName) (ax ^. axiomType)
+    goExpression (Just (ax ^. axiomName)) (ax ^. axiomType)
   StatementFunction f -> goTopFunctionDef modName f
   StatementImport m -> guardNotVisited (m ^. moduleName) (goModule m)
   StatementLocalModule m -> goLocalModule modName m
   StatementInductive i -> do
     checkStartNode (i ^. inductiveName)
     checkBuiltinInductiveStartNode i
     addEdge (i ^. inductiveName) modName
-    mapM_ (goFunctionParameter (i ^. inductiveName)) (i ^. inductiveParameters)
-    goExpression (i ^. inductiveName) (i ^. inductiveType)
+    mapM_ (goFunctionParameter (Just (i ^. inductiveName))) (i ^. inductiveParameters)
+    goExpression (Just (i ^. inductiveName)) (i ^. inductiveType)
     mapM_ (goConstructorDef (i ^. inductiveName)) (i ^. inductiveConstructors)
 
 goTopFunctionDef :: (Members '[State DependencyGraph, State StartNodes, Reader ExportsTable] r) => Name -> FunctionDef -> Sem r ()
@@ -110,22 +128,22 @@ goFunctionDefHelper ::
   Sem r ()
 goFunctionDefHelper f = do
   checkStartNode (f ^. funDefName)
-  goExpression (f ^. funDefName) (f ^. funDefTypeSig)
+  goExpression (Just (f ^. funDefName)) (f ^. funDefTypeSig)
   mapM_ (goFunctionClause (f ^. funDefName)) (f ^. funDefClauses)
 
 -- constructors of an inductive type depend on the inductive type, not the other
 -- way round; an inductive type depends on the types of its constructors
 goConstructorDef :: (Members '[State DependencyGraph, State StartNodes, Reader ExportsTable] r) => Name -> InductiveConstructorDef -> Sem r ()
 goConstructorDef indName c = do
   addEdge (c ^. constructorName) indName
-  goExpression indName (c ^. constructorType)
+  goExpression (Just indName) (c ^. constructorType)
 
 goFunctionClause :: (Members '[State DependencyGraph, State StartNodes, Reader ExportsTable] r) => Name -> FunctionClause -> Sem r ()
 goFunctionClause p c = do
-  mapM_ (goPattern p) (c ^. clausePatterns)
-  goExpression p (c ^. clauseBody)
+  mapM_ (goPattern (Just p)) (c ^. clausePatterns)
+  goExpression (Just p) (c ^. clauseBody)
 
-goPattern :: forall r. (Member (State DependencyGraph) r) => Name -> PatternArg -> Sem r ()
+goPattern :: forall r. (Member (State DependencyGraph) r) => Maybe Name -> PatternArg -> Sem r ()
 goPattern n p = case p ^. patternArgPattern of
   PatternVariable {} -> return ()
   PatternWildcard {} -> return ()
@@ -134,12 +152,17 @@ goPattern n p = case p ^. patternArgPattern of
   where
     goApp :: ConstructorApp -> Sem r ()
     goApp (ConstructorApp ctr ps) = do
-      addEdge n (ctr ^. constructorRefName)
+      addEdgeMay n (ctr ^. constructorRefName)
       mapM_ (goPattern n) ps
 
-goExpression :: forall r. (Members '[State DependencyGraph, State StartNodes, Reader ExportsTable] r) => Name -> Expression -> Sem r ()
+goExpression ::
+  forall r.
+  (Members '[State DependencyGraph, State StartNodes, Reader ExportsTable] r) =>
+  Maybe Name ->
+  Expression ->
+  Sem r ()
 goExpression p e = case e of
-  ExpressionIden i -> addEdge p (idenName i)
+  ExpressionIden i -> addEdgeMay p (idenName i)
   ExpressionUniverse {} -> return ()
   ExpressionFunction f -> do
     goFunctionParameter p (f ^. funParameter)
@@ -177,8 +200,12 @@ goExpression p e = case e of
     goLetClause :: LetClause -> Sem r ()
     goLetClause = \case
       LetFunDef f -> do
-        addEdge p (f ^. funDefName)
+        addEdgeMay p (f ^. funDefName)
         goFunctionDefHelper f
 
-goFunctionParameter :: (Members '[State DependencyGraph, State StartNodes, Reader ExportsTable] r) => Name -> FunctionParameter -> Sem r ()
+goFunctionParameter ::
+  (Members '[State DependencyGraph, State StartNodes, Reader ExportsTable] r) =>
+  Maybe Name ->
+  FunctionParameter ->
+  Sem r ()
 goFunctionParameter p param = goExpression p (param ^. paramType)

src/Juvix/Compiler/Core/Translation/FromInternal.hs

@@ -311,8 +311,9 @@ goFunctionDef ::
   Sem r ()
 goFunctionDef ((f, sym), ty) = do
   mbody <- case f ^. Internal.funDefBuiltin of
-    Just b | isIgnoredBuiltin b -> return Nothing
-    Just _ -> Just <$> runReader initIndexTable (mkFunBody ty f)
+    Just b
+      | isIgnoredBuiltin b -> return Nothing
+      | otherwise -> Just <$> runReader initIndexTable (mkFunBody ty f)
     Nothing -> Just <$> runReader initIndexTable (mkFunBody ty f)
   forM_ mbody (registerIdentNode sym)
   forM_ mbody setIdentArgsInfo'
@@ -461,35 +462,33 @@ goLet ::
   (Members '[InfoTableBuilder, Reader InternalTyped.TypesTable, State InternalTyped.FunctionsTable, Reader Internal.InfoTable, Reader IndexTable] r) =>
   Internal.Let ->
   Sem r Node
-goLet l = do
-  vars <- asks (^. indexTableVars)
-  varsNum <- asks (^. indexTableVarsNum)
-  let bs :: [Name]
-      bs = map (\(Internal.LetFunDef Internal.FunctionDef {..}) -> _funDefName) (toList $ l ^. Internal.letClauses)
-      (vars', varsNum') =
-        foldl'
-          ( \(vs, k) name ->
-              (HashMap.insert (name ^. nameId) k vs, k + 1)
-          )
-          (vars, varsNum)
-          bs
-  (defs, value) <- do
-    values <-
-      mapM
-        ( \(Internal.LetFunDef f) -> do
-            funTy <- goType (f ^. Internal.funDefType)
-
-            funBody <- local (set indexTableVars vars' . set indexTableVarsNum varsNum') (mkFunBody funTy f)
-            return (funTy, funBody)
-        )
-        (l ^. Internal.letClauses)
-
-    lbody <-
-      local
-        (set indexTableVars vars' . set indexTableVarsNum varsNum')
-        (goExpression (l ^. Internal.letExpression))
-    return (values, lbody)
-  return $ mkLetRec' defs value
+goLet l = goClauses (toList (l ^. Internal.letClauses))
+  where
+    goClauses :: [Internal.LetClause] -> Sem r Node
+    goClauses = \case
+      [] -> goExpression (l ^. Internal.letExpression)
+      c : cs -> case c of
+        Internal.LetFunDef f -> goNonRecFun f
+        Internal.LetMutualBlock m -> goMutual m
+        where
+          goNonRecFun :: Internal.FunctionDef -> Sem r Node
+          goNonRecFun f =
+            do
+              funTy <- goType (f ^. Internal.funDefType)
+              funBody <- mkFunBody funTy f
+              rest <- localAddName (f ^. Internal.funDefName) (goClauses cs)
+              return $ mkLet' funTy funBody rest
+          goMutual :: Internal.MutualBlock -> Sem r Node
+          goMutual (Internal.MutualBlock funs) = do
+            let lfuns = toList funs
+                names = map (^. Internal.funDefName) lfuns
+                tys = map (^. Internal.funDefType) lfuns
+            tys' <- mapM goType tys
+            localAddNames names $ do
+              vals' <- sequence [mkFunBody ty f | (ty, f) <- zipExact tys' lfuns]
+              let items = nonEmpty' (zip tys' vals')
+              rest <- goClauses cs
+              return (mkLetRec' items rest)
 
 goAxiomInductive ::
   forall r.

src/Juvix/Compiler/Core/Translation/FromInternal/Data/IndexTable.hs

@@ -14,17 +14,24 @@ makeLenses ''IndexTable
 initIndexTable :: IndexTable
 initIndexTable = IndexTable 0 mempty
 
-localAddName :: forall r a. (Member (Reader IndexTable) r) => Name -> Sem r a -> Sem r a
-localAddName n s = do
+localAddName :: Member (Reader IndexTable) r => Name -> Sem r a -> Sem r a
+localAddName n = localAddNames [n]
+
+localAddNames :: forall r a. (Member (Reader IndexTable) r) => [Name] -> Sem r a -> Sem r a
+localAddNames names s = do
   updateFn <- update
   local updateFn s
   where
+    len :: Int = length names
+    insertMany :: [(NameId, Index)] -> HashMap NameId Index -> HashMap NameId Index
+    insertMany l t = foldl' (\m (k, v) -> HashMap.insert k v m) t l
     update :: Sem r (IndexTable -> IndexTable)
     update = do
       idx <- asks (^. indexTableVarsNum)
+      let newElems = zip (map (^. nameId) names) [idx ..]
       return
-        ( over indexTableVars (HashMap.insert (n ^. nameId) idx)
-            . over indexTableVarsNum (+ 1)
+        ( over indexTableVars (insertMany newElems)
+            . over indexTableVarsNum (+ len)
         )
 
 underBinders :: Members '[Reader IndexTable] r => Int -> Sem r a -> Sem r a

src/Juvix/Compiler/Internal/Data/InfoTable.hs

@@ -73,9 +73,25 @@ extendWithReplExpression e =
   over
     infoFunctions
     ( HashMap.union
-        (HashMap.fromList [(f ^. funDefName, FunctionInfo f) | LetFunDef f <- universeBi e])
+        ( HashMap.fromList
+            [ (f ^. funDefName, FunctionInfo f)
+              | f <- letFunctionDefs e
+            ]
+        )
     )
 
+letFunctionDefs :: Data from => from -> [FunctionDef]
+letFunctionDefs e =
+  concat
+    [ concatMap (toList . flattenClause) _letClauses
+      | Let {..} <- universeBi e
+    ]
+  where
+    flattenClause :: LetClause -> NonEmpty FunctionDef
+    flattenClause = \case
+      LetFunDef f -> pure f
+      LetMutualBlock (MutualBlock fs) -> fs
+
 -- | moduleName ↦ infoTable
 type Cache = HashMap Name InfoTable
 
@@ -117,7 +133,7 @@ buildTable1' m = do
         ]
           <> [ (f ^. funDefName, FunctionInfo f)
                | s <- filter (not . isInclude) ss,
-                 LetFunDef f <- universeBi s
+                 f <- letFunctionDefs s
              ]
       where
         isInclude :: Statement -> Bool

src/Juvix/Compiler/Internal/Extra.hs

@@ -73,9 +73,14 @@ instance HasExpressions Case where
     where
       _caseParens = l ^. caseParens
 
+instance HasExpressions MutualBlock where
+  leafExpressions f (MutualBlock defs) =
+    MutualBlock <$> traverse (leafExpressions f) defs
+
 instance HasExpressions LetClause where
   leafExpressions f = \case
     LetFunDef d -> LetFunDef <$> leafExpressions f d
+    LetMutualBlock b -> LetMutualBlock <$> leafExpressions f b
 
 instance HasExpressions Let where
   leafExpressions f l = do

src/Juvix/Compiler/Internal/Language.hs

@@ -46,7 +46,9 @@ data Statement
 newtype MutualBlock = MutualBlock
   { _mutualFunctions :: NonEmpty FunctionDef
   }
-  deriving stock (Data)
+  deriving stock (Eq, Generic, Data)
+
+instance Hashable MutualBlock
 
 data AxiomDef = AxiomDef
   { _axiomName :: AxiomName,
@@ -98,8 +100,10 @@ data TypedExpression = TypedExpression
     _typedExpression :: Expression
   }
 
-newtype LetClause
-  = LetFunDef FunctionDef
+data LetClause
+  = -- | Non-recursive let definition
+    LetFunDef FunctionDef
+  | LetMutualBlock MutualBlock
   deriving stock (Eq, Generic, Data)
 
 instance Hashable LetClause
@@ -367,9 +371,13 @@ instance HasLoc FunctionClause where
 instance HasLoc FunctionDef where
   getLoc f = getLoc (f ^. funDefName) <> getLocSpan (f ^. funDefClauses)
 
+instance HasLoc MutualBlock where
+  getLoc (MutualBlock defs) = getLocSpan defs
+
 instance HasLoc LetClause where
   getLoc = \case
     LetFunDef f -> getLoc f
+    LetMutualBlock f -> getLoc f
 
 instance HasLoc Let where
   getLoc l = getLocSpan (l ^. letClauses) <> getLoc (l ^. letExpression)

src/Juvix/Compiler/Internal/Pretty/Base.hs

@@ -91,8 +91,17 @@ instance PrettyCode Let where
     return $ kwLet <+> letClauses' <+> kwIn <+> letExpression'
 
 instance PrettyCode LetClause where
+  ppCode :: forall r. Member (Reader Options) r => LetClause -> Sem r (Doc Ann)
   ppCode = \case
     LetFunDef f -> ppCode f
+    LetMutualBlock b -> ppMutual b
+    where
+      ppMutual :: MutualBlock -> Sem r (Doc Ann)
+      ppMutual m@(MutualBlock b)
+        | [_] <- toList b = ppCode b
+        | otherwise = do
+            b' <- ppCode m
+            return (kwMutual <+> braces (line <> indent' b' <> line))
 
 ppPipeBlock :: (PrettyCode a, Members '[Reader Options] r, Traversable t) => t a -> Sem r (Doc Ann)
 ppPipeBlock items = vsep <$> mapM (fmap (kwPipe <+>) . ppCode) items