forestia/bevy
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remove reliance on a trait solver inference bug (#18840)

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The parameter `In` of `call_inner` is completely unconstrained by its
arguments and return type. We are only able to infer it by assuming that
the only associated type equal to `In::Param<'_>` is `In::Param<'_>`
itself. It could just as well be some other associated type which only
normalizes to `In::Param<'_>`. This will change with the next-generation
trait solver and was encountered by a crater run
https://github.com/rust-lang/rust/pull/133502-

cc
https://github.com/rust-lang/trait-system-refactor-initiative/issues/168

I couldn't think of a cleaner alternative here. I first tried to just
provide `In` as an explicit type parameter. This is also kinda ugly as I
need to provide a variable number of them and `${ignore(..)}` is
currently still unstable https://github.com/rust-lang/rust/issues/83527.

Sorry for the inconvenience. Also fun that this function exists to avoid
a separate solver bug in the first place 😅
This commit is contained in:
lcnr 2025-04-14 21:55:31 +02:00 committed by François Mockers
parent 495798c00b
commit 2a2ce6e0ba
2 changed files with 4 additions and 2 deletions
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3
crates/bevy_ecs/src/system/exclusive_function_system.rs
View File

@ -284,6 +284,7 @@ macro_rules! impl_exclusive_system_function {
// without using this function. It fails to recognize that `func` // without using this function. It fails to recognize that `func`
// is a function, potentially because of the multiple impls of `FnMut` // is a function, potentially because of the multiple impls of `FnMut`
fn call_inner<In: SystemInput, Out, $($param,)*>( fn call_inner<In: SystemInput, Out, $($param,)*>(
_: PhantomData<In>,
mut f: impl FnMut(In::Param<'_>, &mut World, $($param,)*) -> Out, mut f: impl FnMut(In::Param<'_>, &mut World, $($param,)*) -> Out,
input: In::Inner<'_>, input: In::Inner<'_>,
world: &mut World, world: &mut World,
@ -292,7 +293,7 @@ macro_rules! impl_exclusive_system_function {
f(In::wrap(input), world, $($param,)*) f(In::wrap(input), world, $($param,)*)
} }
let ($($param,)*) = param_value; let ($($param,)*) = param_value;
call_inner(self, input, world, $($param),*) call_inner(PhantomData::<In>, self, input, world, $($param),*)
} }
} }
}; };

3
crates/bevy_ecs/src/system/function_system.rs
View File

@ -972,6 +972,7 @@ macro_rules! impl_system_function {
#[inline] #[inline]
fn run(&mut self, input: In::Inner<'_>, param_value: SystemParamItem< ($($param,)*)>) -> Out { fn run(&mut self, input: In::Inner<'_>, param_value: SystemParamItem< ($($param,)*)>) -> Out {
fn call_inner<In: SystemInput, Out, $($param,)*>( fn call_inner<In: SystemInput, Out, $($param,)*>(
_: PhantomData<In>,
mut f: impl FnMut(In::Param<'_>, $($param,)*)->Out, mut f: impl FnMut(In::Param<'_>, $($param,)*)->Out,
input: In::Inner<'_>, input: In::Inner<'_>,
$($param: $param,)* $($param: $param,)*
@ -979,7 +980,7 @@ macro_rules! impl_system_function {
f(In::wrap(input), $($param,)*) f(In::wrap(input), $($param,)*)
} }
let ($($param,)*) = param_value; let ($($param,)*) = param_value;
call_inner(self, input, $($param),*) call_inner(PhantomData::<In>, self, input, $($param),*)
} }
} }
}; };