+ add test for already fixed #39844

tests/webtbs/tw39844.pp

@@ -0,0 +1,24 @@
+program tw39844;
+{$mode objfpc} {$typedaddress on} {$modeswitch typehelpers} {$coperators on}
+type
+	XType = double;
+
+	XTypeHelper = type helper for XType
+		procedure Add(x: XType); inline;
+	end;
+
+	procedure XTypeHelper.Add(x: XType);
+	begin
+		self += x;
+	end;
+
+var
+	x: XType;
+
+begin
+	x := 0;
+	(@x)^.Add(1);
+	if x <> 1 then begin writeln('x = ', x, ', expected 1'); halt(1); end;
+	writeln('ok');
+end.
+