Refactoring Binder

ASTPlayground/ASTPlayground.dproj

@@ -4,7 +4,7 @@
         <ProjectVersion>20.3</ProjectVersion>
         <FrameworkType>FMX</FrameworkType>
         <Base>True</Base>
-        <Config Condition="'$(Config)'==''">Release</Config>
+        <Config Condition="'$(Config)'==''">Debug</Config>
         <Platform Condition="'$(Platform)'==''">Win64</Platform>
         <ProjectName Condition="'$(ProjectName)'==''">ASTPlayground</ProjectName>
         <TargetedPlatforms>2</TargetedPlatforms>

Src/AST/Myc.Ast.Binding.pas

@@ -12,7 +12,7 @@ uses
     Myc.Ast.Scope;
 
 type
-    TAstBinder = class(TAstTraverser<Boolean>)
+    TAstBinder = class(TAstTraverser)
         type
             TUpvalueMapping = class
                 Map: TDictionary<TResolvedAddress, Integer>;
@@ -25,12 +25,13 @@ type
         FCurrentDescriptor: IScopeDescriptor;
         FUpvalueStack: TStack<TUpvalueMapping>;
         FNestedLambdaCount: Integer;
+        FIsTailStack: TStack<Boolean>;
         FNextIsTail: Boolean;
         procedure EnterScope;
         procedure ExitScope;
 
     protected
-        function EnterNode(const Node: IAstNode): Boolean; override;
+        function Accept(const Node: IAstNode): TDataValue; override;
 
     public
         constructor Create(const AInitialScope: IExecutionScope);
@@ -51,7 +52,6 @@ type
         function VisitAssignment(const Node: IAssignmentNode): TDataValue; override;
 
         property CurrentDescriptor: IScopeDescriptor read FCurrentDescriptor;
-        property NextIsTail: Boolean write FNextIsTail;
     end;
 
 implementation
@@ -61,12 +61,6 @@ uses
     Myc.Ast;
 
 type
-    TResolvedAddressComparer = class(TEqualityComparer<TResolvedAddress>)
-    public
-        function Equals(const Left, Right: TResolvedAddress): Boolean; override;
-        function GetHashCode(const Value: TResolvedAddress): Integer; override;
-    end;
-
     TScopeDescriptor = class(TInterfacedObject, IScopeDescriptor)
     private
         FParent: IScopeDescriptor;
@@ -84,22 +78,6 @@ type
         property Symbols: TDictionary<string, Integer> read FSymbols;
     end;
 
-{ TResolvedAddressComparer }
-
-function TResolvedAddressComparer.Equals(const Left, Right: TResolvedAddress): Boolean;
-begin
-    Result := (Left.Kind = Right.Kind) and (Left.ScopeDepth = Right.ScopeDepth) and (Left.SlotIndex = Right.SlotIndex);
-end;
-
-function TResolvedAddressComparer.GetHashCode(const Value: TResolvedAddress): Integer;
-begin
-    // Simple combining hash function
-    Result := 17;
-    Result := Result * 23 + Ord(Value.Kind);
-    Result := Result * 23 + Value.ScopeDepth;
-    Result := Result * 23 + Value.SlotIndex;
-end;
-
 { TAstBinder }
 
 constructor TAstBinder.Create(const AInitialScope: IExecutionScope);
@@ -108,15 +86,31 @@ begin
     FCurrentDescriptor := CreateDescriptor(AInitialScope);
     FUpvalueStack := TObjectStack<TUpvalueMapping>.Create(true);
     FNestedLambdaCount := 0;
-    FNextIsTail := False;
+    FIsTailStack := TStack<Boolean>.Create;
+    // The content of the root node is in a tail position.
+    FNextIsTail := true;
 end;
 
 destructor TAstBinder.Destroy;
 begin
+    FIsTailStack.Free;
     FUpvalueStack.Free;
     inherited;
 end;
 
+function TAstBinder.Accept(const Node: IAstNode): TDataValue;
+begin
+    if not Assigned(Node) or Done then
+        exit;
+
+    FIsTailStack.Push(FNextIsTail);
+    try
+        Result := inherited Accept(Node);
+    finally
+        FNextIsTail := FIsTailStack.Pop;
+    end;
+end;
+
 class function TAstBinder.Bind(const RootNode: IAstNode; const ParentScope: IExecutionScope): IScopeDescriptor;
 var
     binder: TAstBinder;
@@ -125,7 +119,7 @@ begin
     try
         binder.EnterScope;
         try
-            // Start the traversal. The content of the root node is in a tail position.
+            // Start the traversal
             binder.Accept(RootNode);
             Result := binder.CurrentDescriptor;
         finally
@@ -158,12 +152,6 @@ begin
     FCurrentDescriptor := FCurrentDescriptor.Parent;
 end;
 
-function TAstBinder.EnterNode(const Node: IAstNode): Boolean;
-begin
-    // The context for the current node is whatever the parent Visit... method prepared.
-    Result := FNextIsTail;
-end;
-
 function TAstBinder.VisitAssignment(const Node: IAssignmentNode): TDataValue;
 begin
     FNextIsTail := False;
@@ -177,27 +165,24 @@ begin
 end;
 
 function TAstBinder.VisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
-var
-    i: Integer;
 begin
-    for i := 0 to Node.Expressions.Count - 2 do
+    FNextIsTail := False;
-    begin
-        FNextIsTail := False;
-        Accept(Node.Expressions[i]);
-    end;
 
-    if Node.Expressions.Count > 0 then
+    var n := Node.Expressions.Count - 1;
+    for var i := 0 to n do
     begin
         // The last expression is in a tail position IF the block itself is.
-        FNextIsTail := Data.Peek;
+        if i = n then
-        Accept(Node.Expressions.Last);
+            FNextIsTail := FIsTailStack.Peek;
+
+        Accept(Node.Expressions[i]);
     end;
 end;
 
 function TAstBinder.VisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
 begin
     // Annotate this node based on its context, which is on top of the stack.
-    (Node as TFunctionCallNode).IsTailCall := Data.Peek;
+    (Node as TFunctionCallNode).IsTailCall := FIsTailStack.Peek;
 
     // Let the default traverser visit children (callee, args), but ensure
     // their context is non-tail.
@@ -250,7 +235,7 @@ begin
     Accept(Node.Condition);
 
     // The branches are in a tail position if the if-expression itself is.
-    FNextIsTail := Data.Peek;
+    FNextIsTail := FIsTailStack.Peek;
     Accept(Node.ThenBranch);
     if Assigned(Node.ElseBranch) then
         Accept(Node.ElseBranch);
@@ -266,14 +251,13 @@ begin
     try
         EnterScope;
         try
-            (FCurrentDescriptor as TScopeDescriptor).Define('Self');
+            FCurrentDescriptor.Define('Self');
 
             for param in Node.Parameters do
-                (FCurrentDescriptor as TScopeDescriptor).Define(param.Name);
+                FCurrentDescriptor.Define(param.Name);
 
             var lastNestedLambdaCount := FNestedLambdaCount;
 
-            // Manually traverse children since we can't call 'inherited' from the simple traverser.
             // Parameters are never in a tail position.
             FNextIsTail := False;
             for param in Node.Parameters do
@@ -290,22 +274,23 @@ begin
         end;
     finally
         var upvalue := FUpvalueStack.Peek;
+        try
+            sortedPairs := upvalue.Map.ToArray;
+            TArray.Sort<TPair<TResolvedAddress, Integer>>(
+                sortedPairs,
+                TComparer<TPair<TResolvedAddress, Integer>>.Construct(
+                    function(const Left, Right: TPair<TResolvedAddress, Integer>): Integer begin Result := Left.Value - Right.Value; end
+                )
+            );
 
-        sortedPairs := upvalue.Map.ToArray;
+            SetLength(sourceAddresses, Length(sortedPairs));
-        TArray.Sort<TPair<TResolvedAddress, Integer>>(
+            for var i := 0 to High(sortedPairs) do
-            sortedPairs,
+                sourceAddresses[i] := sortedPairs[i].Key;
-            TComparer<TPair<TResolvedAddress, Integer>>.Construct(
-                function(const Left, Right: TPair<TResolvedAddress, Integer>): Integer begin Result := Left.Value - Right.Value; end
-            )
-        );
 
-        SetLength(sourceAddresses, Length(sortedPairs));
+            (Node as TLambdaExpressionNode).Upvalues := sourceAddresses;
-        for var i := 0 to High(sortedPairs) do
+        finally
-            sourceAddresses[i] := sortedPairs[i].Key;
+            FUpvalueStack.Pop;
-
+        end;
-        (Node as TLambdaExpressionNode).Upvalues := sourceAddresses;
-
-        FUpvalueStack.Pop;
 
         inc(FNestedLambdaCount);
     end;
@@ -318,7 +303,7 @@ begin
     Accept(Node.Condition);
 
     // The branches are in a tail position if the ternary expression itself is.
-    FNextIsTail := Data.Peek;
+    FNextIsTail := FIsTailStack.Peek;
     Accept(Node.ThenBranch);
     Accept(Node.ElseBranch);
 end;
@@ -338,7 +323,7 @@ begin
     if Assigned(Node.Initializer) then
         Accept(Node.Initializer);
 
-    slotIndex := (FCurrentDescriptor as TScopeDescriptor).Define(Node.Identifier.Name);
+    slotIndex := FCurrentDescriptor.Define(Node.Identifier.Name);
     (Node.Identifier as TIdentifierNode).Address := TResolvedAddress.Create(akLocalOrParent, 0, slotIndex);
 
     FNextIsTail := False;
@@ -412,7 +397,7 @@ end;
 constructor TAstBinder.TUpvalueMapping.Create;
 begin
     inherited Create;
-    Map := TDictionary<TResolvedAddress, Integer>.Create(TResolvedAddressComparer.Default);
+    Map := TDictionary<TResolvedAddress, Integer>.Create;
     Nodes := TList<IIdentifierNode>.Create();
 end;