Nop-Node

Src/AST/Myc.Ast.pas

@@ -28,6 +28,10 @@ type
         class procedure RegisterLibrary(const AProc: TRegisterLibraryProc); static;
         class function CreateScope(Parent: IExecutionScope; const Descriptor: IScopeDescriptor = nil): IExecutionScope; static;
 
+        // A No-Operation node, used as a placeholder/stub (e.g., for UI drop targets).
+        // This node is illegal in the compiler (Binder/TypeChecker will reject it).
+        class function Nop: IAstNode; static;
+
         // --- Factory functions ---
         class function Constant(const AValue: TDataValue): IConstantNode; overload; static;
         class function Constant(const AValue: String): IConstantNode; overload; static;
@@ -103,6 +107,7 @@ type
         function AsAddSeriesItem: IAddSeriesItemNode; virtual;
         function AsSeriesLength: ISeriesLengthNode; virtual;
         function AsRecur: IRecurNode; virtual;
+        function AsNop: INopNode; virtual; // Added Nop
 
         property StaticType: IStaticType read FStaticType write SetStaticType;
         property Kind: TAstNodeKind read GetKind;
@@ -474,6 +479,17 @@ implementation
 uses
     System.Generics.Defaults;
 
+// Added Nop
+type
+    TNopNode = class(TAstNode, INopNode)
+    private
+        function GetKind: TAstNodeKind; override;
+    public
+        constructor Create;
+        function Accept(const Visitor: IAstVisitor): TDataValue; override;
+        function AsNop: INopNode; override;
+    end;
+
 { TAst }
 
 class function TAst.CreateScope(Parent: IExecutionScope; const Descriptor: IScopeDescriptor): IExecutionScope;
@@ -603,6 +619,12 @@ begin
     Result := TMemberAccessNode.Create(ABase, AMember);
 end;
 
+class function TAst.Nop: IAstNode;
+begin
+    // Factory function for the new Nop node
+    Result := TNopNode.Create;
+end;
+
 class function TAst.Quasiquote(const AExpression: IAstNode): IQuasiquoteNode;
 begin
     Result := TQuasiquoteNode.Create(AExpression);
@@ -650,6 +672,30 @@ begin
     Result := TVariableDeclarationNode.Create(AIdentifier, AInitializer);
 end;
 
+{ TNopNode }
+
+constructor TNopNode.Create;
+begin
+    inherited Create;
+    // Nop nodes are 'Void' by default, though TypeChecker will reject them anyway.
+    StaticType := TTypes.Void;
+end;
+
+function TNopNode.Accept(const Visitor: IAstVisitor): TDataValue;
+begin
+    Result := Visitor.VisitNop(Self);
+end;
+
+function TNopNode.AsNop: INopNode;
+begin
+    Result := Self;
+end;
+
+function TNopNode.GetKind: TAstNodeKind;
+begin
+    Result := akNop;
+end;
+
 { TAstNode }
 
 constructor TAstNode.Create;
@@ -733,6 +779,12 @@ begin
     raise ETypeException.Create('Node is not a MemberAccess');
 end;
 
+function TAstNode.AsNop: INopNode;
+begin
+    // Added Nop implementation
+    raise ETypeException.Create('Node is not a Nop');
+end;
+
 function TAstNode.AsQuasiquote: IQuasiquoteNode;
 begin
     raise ETypeException.Create('Node is not a Quasiquote');