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Revise docs for system set marker traits (#7882)

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# Objective

#7863 introduced a potential footgun. When trying to incorrectly add a user-defined type using `in_base_set`, the compiler will suggest that the user implement `BaseSystemSet` for their type. This is a reasonable-sounding suggestion, however this is not the correct way to make a base set, and will lead to a confusing panic message when a marker trait is implemented for the wrong type.

## Solution

Rewrite the documentation for these traits, making it more clear that `BaseSystemSet` is a marker for types that are already base sets, and not a way to define a base set.
This commit is contained in:
JoJoJet 2023-03-03 14:43:54 +00:00
parent 73c1ab1d42
commit 85c8fb9dfa
1 changed files with 9 additions and 5 deletions
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14
crates/bevy_ecs/src/schedule/set.rs
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@ -37,14 +37,18 @@ pub trait SystemSet: DynHash + Debug + Send + Sync + 'static {
fn dyn_clone(&self) -> Box<dyn SystemSet>;
}
/// A system set that is never contained in another set.
/// Systems and other system sets may only belong to one base set.
/// A marker trait for `SystemSet` types where [`is_base`] returns `true`.
/// This should only be implemented for types that satisfy this requirement.
/// It is automatically implemented for base set types by `#[derive(SystemSet)]`.
///
/// This should only be implemented for types that return `true` from [`SystemSet::is_base`].
/// [`is_base`]: SystemSet::is_base
pub trait BaseSystemSet: SystemSet {}
/// System sets that are *not* base sets. This should not be implemented for
/// any types that implement [`BaseSystemSet`].
/// A marker trait for `SystemSet` types where [`is_base`] returns `false`.
/// This should only be implemented for types that satisfy this requirement.
/// It is automatically implemented for non-base set types by `#[derive(SystemSet)]`.
///
/// [`is_base`]: SystemSet::is_base
pub trait FreeSystemSet: SystemSet {}
impl PartialEq for dyn SystemSet {