`needless_pass_by_value` FP that errors once actioned because of trait bounds (Bevy)

Summary

When using the Bevy ECS game engine, "systems" are defined as a function with parameters. Bevy also has wrapper types around & references: Res<T> (at least, that's how I understand it), that are used as parameters to systems.

The needless_pass_by_value lint is triggered by the Res<T> type; however, actioning the lint by making it &Res<T> will result in compilation errors because of the trait bounds on the functions that consume the function definition (in order to register the system), e.g. App::add_startup_system.

Lint Name

needless_pass_by_value

Reproducer

I tried this code:

Cargo.toml:

[package]
name = "untitled"
version = "0.1.0"
edition = "2021"

[dependencies]
bevy = "0.7.0"

main.rs:

#![warn(clippy::needless_pass_by_value)]

use bevy::prelude::*;

fn main() {
    App::new().add_startup_system(spawn);
}

fn spawn(assets: Res<AssetServer>) {
    let _: Handle<Mesh> = assets.load("");
}

I saw this happen:

    Checking untitled v0.1.0 (D:\dev\git\untitled)
warning: this argument is passed by value, but not consumed in the function body
 --> src\main.rs:9:18
  |
9 | fn spawn(assets: Res<AssetServer>) {
  |                  ^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `&Res<AssetServer>`
  |
note: the lint level is defined here
 --> src\main.rs:1:9
  |
1 | #![warn(clippy::needless_pass_by_value)]
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_value

warning: `untitled` (bin "untitled") generated 1 warning
    Finished dev [unoptimized + debuginfo] target(s) in 0.53s

I expected to see this happen:

    Checking untitled v0.1.0 (D:\dev\git\untitled)
    Finished dev [unoptimized + debuginfo] target(s) in 0.54s

If I change Res<AssetServer> to &Res<AssetServer>:

error[E0277]: the trait bound `for<'r, 's> fn(&'r bevy::prelude::Res<'s, bevy::prelude::AssetServer>) {spawn}: bevy::prelude::IntoSystem<(), (), _>` is not satisfied
   --> src\main.rs:6:35
    |
6   |     App::new().add_startup_system(spawn);
    |                ------------------ ^^^^^ the trait `bevy::prelude::IntoSystem<(), (), _>` is not implemented for `for<'r, 's> fn(&'r bevy::prelude::Res<'s, bevy::prelude::AssetServer>) {spawn}`
    |                |
    |                required by a bound introduced by this call
    |
    = note: required because of the requirements on the impl of `bevy::ecs::schedule::IntoSystemDescriptor<_>` for `for<'r, 's> fn(&'r bevy::prelude::Res<'s, bevy::prelude::AssetServer>) {spawn}`
note: required by a bound in `bevy::prelude::App::add_startup_system`
   --> C:\Users\jdsmi\.cargo\registry\src\github.com-1ecc6299db9ec823\bevy_app-0.7.0\src\app.rs:436:22
    |
436 |         system: impl IntoSystemDescriptor<Params>,
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `bevy::prelude::App::add_startup_system`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `untitled` due to previous error

Version

rustc 1.61.0 (fe5b13d68 2022-05-18)
binary: rustc
commit-hash: fe5b13d681f25ee6474be29d748c65adcd91f69e
commit-date: 2022-05-18
host: x86_64-pc-windows-msvc
release: 1.61.0
LLVM version: 14.0.0

Additional Labels

@rustbot label +I-suggestion-causes-error

Start with the needless_pass_by_value lint implementation and its tests, then reproduce the report using the Cargo.toml and main.rs example with Bevy 0.7.0. Trace the suggested &Res<AssetServer> signature against App::add_startup_system and its IntoSystem bound; done means the lint no longer produces an action that fails to compile.