Nicola Papale 71a246ce9e Improve QueryIter size_hint hints (#4244) ... ## Objective This fixes #1686. `size_hint` can be useful even if a little niche. For example, `collect::<Vec<_>>()` uses the `size_hint` of Iterator it collects from to pre-allocate a memory slice large enough to not require re-allocating when pushing all the elements of the iterator. ## Solution To this effect I made the following changes: * Add a `IS_ARCHETYPAL` associated constant to the `Fetch` trait, this constant tells us when it is safe to assume that the `Fetch` relies exclusively on archetypes to filter queried entities * Add `IS_ARCHETYPAL` to all the implementations of `Fetch` * Use that constant in `QueryIter::size_hint` to provide a more useful ## Migration guide The new associated constant is an API breaking change. For the user, if they implemented a custom `Fetch`, it means they have to add this associated constant to their implementation. Either `true` if it doesn't limit the number of entities returned in a query beyond that of archetypes, or `false` for when it does.		2022-04-27 18:02:06 +00:00
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src	Improve QueryIter size_hint hints (#4244)	2022-04-27 18:02:06 +00:00
Cargo.toml	Bump Bevy to 0.8.0-dev (#4505)	2022-04-17 23:04:52 +00:00