Loc.Errors is a second exception, and the handlers in the session and the
daemon name only Loc.Error — so a list reaching them is an unhandled
exception and a dead session, which is the one thing the dev loop exists to
prevent. A flag on the function the session already calls left that one
label away from happening. Parse.program_all and Check.program_all are
separate names, so the session's call site has to be edited by a person for
its behaviour to change, and the guarantee stops being a default argument.
Placeless diagnostics now sort last rather than first. A wrong main signature
is raised against unknown, which is line 0, and sorting on the number alone
put it above every error that can actually be clicked. It is a real error and
it is not anywhere, so it goes after the ones that are.