Alice Cecile 509548190b Add get_multiple and get_multiple_mut APIs for Query and QueryState (#4298) ... # Objective - The inability to have multiple active mutable borrows into a query is a common source of borrow-checker pain for users. - This is a pointless restriction if and only if we can guarantee that the entities they are accessing are unique. - This could already by bypassed with get_unchecked, but that is an extremely unsafe API. - Closes https://github.com/bevyengine/bevy/issues/2042. ## Solution - Add `get_multiple`, `get_multiple_mut` and their unchecked equivalents (`multiple` and `multiple_mut`) to `Query` and `QueryState`. - Improve the `QueryEntityError` type to provide more useful error information. ## Changelog - Added `get_multiple`, `get_multiple_mut` and their unchecked equivalents (`multiple` and `multiple_mut`) to Query and QueryState. ## Migration Guide - The `QueryEntityError` enum now has a `AliasedMutability variant, and returns the offending entity. ## Context This is a fresh attempt at #3333; rebasing was behaving very badly and it was important to rebase on top of the recent query soundness fixes. Many thanks to all the reviewers in that thread, especially @BoxyUwU for the help with lifetimes. ## To-do - [x] Add compile fail tests - [x] Successfully deduplicate code - [x] Decide what to do about failing doc tests - [x] Get some reviews for lifetime soundness		2022-03-30 19:16:48 +00:00
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ui	Add get_multiple and get_multiple_mut APIs for Query and QueryState (#4298)	2022-03-30 19:16:48 +00:00
ui.rs	Assert compiler errors for compile_fail tests (#3067)	2021-11-13 22:43:19 +00:00