Clippy needless_pass_by_value false positive

[DaAlbrecht]

The getting-started example from bevy looks like this

use bevy::prelude::*;

#[derive(Component)]
struct Person;

#[derive(Component)]
struct Name(String);

fn main() {
    App::new().add_systems(Update, greet_people).run();
}

fn greet_people(query: Query<&Name, With<Person>>) {
    for name in &query {
        println!("hello {}!", name.0);
    }
}

resulting in the following false positive of the pedantic needless-pass-by-value clippy lint.

warning: this argument is passed by value, but not consumed in the function body
  --> src/main.rs:13:24
   |
13 | fn greet_people(query: Query<&Name, With<Person>>) {
   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `&Query<&Name, With<Person>>`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_value
   = note: `-W clippy::needless-pass-by-value` implied by `-W clippy::pedantic`
   = help: to override `-W clippy::pedantic` add `#[allow(clippy::needless_pass_by_value)]`

If you follow the advice you get the following

use bevy::prelude::*;

#[derive(Component)]
struct Person;

#[derive(Component)]
struct Name(String);

fn main() {
    App::new().add_systems(Update, greet_people).run();
}

fn greet_people(query: &Query<&Name, With<Person>>) {
    for name in &query {
        println!("hello {}!", name.0);
    }
}

error[E0277]: `fn(&Query<'b, 'c, &Name, With<Person>>) {greet_people}` does not describe a valid system configuration
   --> src/main.rs:10:36
    |
10  |     App::new().add_systems(Update, greet_people).run();
    |                -----------         ^^^^^^^^^^^^ invalid system configuration
    |                |
    |                required by a bound introduced by this call
    |
    = note: the full name for the type has been written to '/private/tmp/demo_lint/target/debug/deps/demo_lint-3b418e1522fada65.long-type-10272769760713719372.txt'
    = note: consider using `--verbose` to print the full type name to the console
    = help: the trait `IntoSystem<(), (), _>` is not implemented for fn item `fn(&Query<'b, 'c, &Name, With<Person>>) {greet_people}`
    = help: the following other types implement trait `IntoSystem<In, Out, Marker>`:
              `IntoAdapterSystem<Func, S>` implements `IntoSystem<<Func as Adapt<<S as IntoSystem<I, O, M>>::System>>::In, <Func as Adapt<<S as IntoSystem<I, O, M>>::System>>::Out, (IsAdapterSystemMarker, I, O, M)>`
              `IntoPipeSystem<A, B>` implements `IntoSystem<IA, OB, (IsPipeSystemMarker, OA, IB, MA, MB)>`
    = note: required for `fn(&Query<'b, 'c, &Name, With<Person>>) {greet_people}` to implement `IntoSystemConfigs<_>`
note: required by a bound in `bevy::prelude::App::add_systems`

While this is only a pedantic lint I still think it's a great one and I have already seen multiple posts about bevy and this lint as shown here: rust-lang/rust-clippy#8940

[BD103]

For context, please see this comment: #276 (comment)

We can likely copy Clippy's needless_pass_by_value code to implement this lint. To make it work for Bevy-specific types, we should modify it to not emit a lint if the parameter implements SystemParam.

I'm not sure I like the idea of completely ripping the lint and being forced to maintain it ourselves, but I also can't see rust-lang/rust-clippy#8940 reasonably being being fixed, as it would have to check every single place each function is referenced.

[DaAlbrecht]

For context, please see this comment: #276 (comment)

We can likely copy Clippy's needless_pass_by_value code to implement this lint. To make it work for Bevy-specific types, we should modify it to not emit a lint if the parameter implements SystemParam.

I'm not sure I like the idea of completely ripping the lint and being forced to maintain it ourselves, but I also can't see rust-lang/rust-clippy#8940 reasonably being being fixed, as it would have to check every single place each function is referenced.

Being forced to maintain the lint ourselves is kinda unfortunate but it would at least be a pretty easy fix. But since its only of the category pedantic its completely fine for me if we don't do it.