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[Merged by Bors] - Make the SystemParam derive macro more flexible #6694

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[Merged by Bors] - Make the SystemParam derive macro more flexible #6694

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2e5ce49
relax restrictions on `SystemParam` lifetimes
joseph-gio Nov 19, 2022
89cc5c6
update some examples
joseph-gio Nov 19, 2022
9a8e8bd
remove the extra lifetime from `EventWriter`
joseph-gio Nov 19, 2022
20bb726
silence a lint
joseph-gio Nov 19, 2022
8d0017c
use marker
joseph-gio Nov 19, 2022
fb27c48
Clarify a limitation
joseph-gio Nov 19, 2022
02613c5
improve the error message when lifetimes are incorrect
joseph-gio Nov 19, 2022
d122be9
rename a field
joseph-gio Nov 19, 2022
1d25b81
rewrite a comment
joseph-gio Nov 19, 2022
163fa9d
Merge remote-tracking branch 'upstream/main' into system-param-lifetimes
joseph-gio Nov 28, 2022
679fd1c
add more information to lifetime errors
joseph-gio Nov 28, 2022
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11 changes: 8 additions & 3 deletions crates/bevy_ecs/macros/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -380,9 +380,14 @@ pub fn derive_system_param(input: TokenStream) -> TokenStream {
let w = format_ident!("w");
let s = format_ident!("s");
if ident != &w && ident != &s {
return syn::Error::new_spanned(lt, "invalid lifetime name: expected `'w` or `'s`")
.into_compile_error()
.into();
return syn::Error::new_spanned(
lt,
r#"invalid lifetime name: expected `'w` or `'s`
'w -- refers to data stored in the World.
's -- refers to data stored in the SystemParam's state.'"#,
)
.into_compile_error()
.into();
Comment on lines +383 to +390
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@james7132 do you think this is an improvement?

This usage is called out in the docs, but IMO the best way of teaching this is to just let users do it wrong, then have the error tell them the right way of doing it.

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Looks much better to me. Thanks!

}
}

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