Statement Expressions landed in FPC trunk

[fibodevy]

A bit over a year after the merge request was opened (Jun 14, 2025), Statement Expressions have been merged into FPC trunk: https://gitlab.com/freepascal.org/fpc/source/-/merge_requests/1037

Unleashed Pascal picked this feature up from that merge request early on, so if, case and try as expressions have been available here for a while. The version that got merged upstream differs a bit from what is in Unleashed right now. The main visible difference is syntax: a case expression with an else branch and a try-except expression now close with the end keyword, e.g. s := case x of 1: 'one'; else 'other' end;. In Unleashed the else expression is currently the last token and there is no end. Upstream also added anonymous functions as branch values, a wider set of result type unification rules (common class ancestor, interfaces, nil vs class, variants), dedicated error messages, and the modeswitch is on by default in {$mode delphi}.

Plan: first I will update the Statement Expressions feature so it is 100% compatible with the FPC version (the end closing form in case/try plus a couple of smaller things). After that, a full sync of the fork with FPC trunk. There are only about 300 upstream commits since the last sync point, most of them small fixes, so I do not expect trouble there.

[fibodevy]

Update: the compiler side is done. Statement Expressions in Unleashed now match the upstream version 1:1 - case with an else branch and try-except expressions close with end, and the remaining smaller differences are gone as well, so code written against the FPC trunk syntax compiles here unchanged.

That leaves the sync of the fork with trunk. Getting the feature itself aligned turned out to be simpler than expected, so the groundwork is in place. Pulling in the rest of the upstream commits will take a little longer, though - that part is not done yet and will land in a later step.