No longer possible to return nil object from Delphi side

[Anders Melander]

After 508af9c it is no longer possible to return a nil object reference from Delphi side.

Test case

Script

var MyObject := SomeFunctionReturningAnObject; // Causes assertion failure

Delphi side

procedure TDataModuleBlah.dwsUnitBlahFunctionsSomeFunctionReturningAnObjectEval(Info: TProgramInfo; ExtObject: TObject);
begin
  Info.ResultAsVariant := Unassigned; // Return a nil object reference to script
end;

---

The problem is with TProgramExpr.EvalAsScriptObj:

// EvalAsScriptObj
//
procedure TProgramExpr.EvalAsScriptObj(exec : TdwsExecution; var Result : IScriptObj);
var
   buf : Variant;
begin
   EvalAsVariant(exec, buf);
   Assert(VarType(buf)=varUnknown);
   Result:=(IUnknown(TVarData(buf).VUnknown) as IScriptObj);
end;

The ASSERT should read:

   Assert((VarType(buf)=varEmpty) or (VarType(buf)=varUnknown));

[Eric Grange]

This was an error: Unassigned is distinct from a nil object (and both nil and Unassigned are distinct from Null)

To return a nil you should pass either an IUnknown(nil) or IScriptObj(nil)

[Anders Melander]

Got it. Thanks.