Add Lints disallow_fixed_update and disallow_update

[DaAlbrecht]

closes #99

[BD103]

Here's a "fun" thing I just realized, the following code isn't caught by the linter:

#![deny(bevy::disallow_update)]

fn update() -> impl ScheduleLabel {
    Update
}

fn main() {
    // Adding system to `Update` schedule, but no error is emitted.
    App::new().add_systems(update(), my_system);
}

impl ScheduleLabel is seen as an TyKind::Alias, which isn't caught in match_type(). We need to resolve the type again in order to get the final, concrete type:

if let TyKind::Alias(_, alias) = schedule_ty.kind() {
    schedule_ty = cx.tcx.type_of(alias.def_id);
}

This isn't something you need to handle now, but we may need to eventually check for it in every single lint (oof). I'd like to wait until after #456 before messing with type path matching more, though.

[DaAlbrecht]

hahah nice catch! whoever writes update() is just evil ^^

[BD103]

It should be good to go now!

[DaAlbrecht]

It should be good to go now!

😢 it was not. Missing ignore for the doctests (or importing bevy::prelude::*). Will fix when im home if you dont beat me to it

[BD103]

It should be good to go now!

😢 it was not. Missing ignore for the doctests (or importing bevy::prelude::*). Will fix when im home if you dont beat me to it

I might have beaten you to it >:D