Specify lifetimes in system arguments

[dimvoly]

I have a system:

pub fn cursor_hover(
    raycast_source_query: Query<&RaycastSource<PickingRaycastSet>>,
) {
 if let Some(intersection) = unwrap_everything(
	&raycast_source_query,
    ) 
    {
    // do stuff with intersection:&IntersectionData
    }
}

Within that system, some of the queries are processed in a second function, which returns references:

fn unwrap_everything<'a>(
    raycast_source_query: &'a Query<'a, 'a, &'a RaycastSource<PickingRaycastSet>>,
) -> Option<(
    &'a IntersectionData,
)> {
  // ... retrieves the IntersectionData, which comes back as a reference
}

I tried specifying lifetime parameters, but if you follow what the compiler tells you, you end up with lifetime specifiers on the system itself which the compiler objects to also.

What is the way to specifying lifetime parameters such that the second function returns references?

I have multiple things being returned in unwrap_everything, so am not keen to call .clone() on each of them.

If I get rid of the unwrap_everything and process everything inline, everything is fine, I can use the references. But that results in rather messy code.

[dimvoly]

Why do these things decide to work immediately after me asking the question? Have just tried the following:

fn unwrap_everything<'a, 'b, 'c, 'd>(
    raycast_source_query: &'a Query<'b, 'c, &'d RaycastSource<PickingRaycastSet>>,
) -> Option<(
    &'a IntersectionData,
)> {
  // ... retrieves the IntersectionData, which comes back as a reference
}

That compiles. No doubt a bunch of these are redundant so I'll play around with it further.

This does not require lifetime parameters on the system itself, only this function. Presumably they're inferred by the compiler for the system.

[dimvoly]

Have ultimately ended up with this in the argument:
raycast_source_query: &'a Query<'_, '_, &'b RaycastSource<PickingRaycastSet>>,