Hmm, fshcomp appears to have been untouched for a very long time. 2009 ?
Its likely you will need to update something in it if it no one else has for twelve years.
So, look in sreditcur.pas, line 294, column 19, Lazarus will have highlighted that for you already. That line calls RightLean(Self);, 'Self is, at this stage, TSrEditCur but the declaration at line 41 expects a TCustomEdit -
procedure RightLean(var xe: TCustomEdit);
I have no idea whats going on here and it seems unlikely the original author is still active so it looks like you have a bit of debugging to do ! As a start, I cast 'Selt' to a TCustomEdit and it compiled.
RightLean(TCustomEdit(Self));
But as I am not going to add the unit to my install, I am creating the component "on the fly" and did not see any component popping up. Setting sensible positions and visibility did not help so, I am afraid, its up to you. If you do get it going as expected, please remember to put a patch into Mantis so it gets fixed. If you cannot make any progress, you could put just a bug report into Mantis ?
Good luck !
Davo