[diagnostics] Add mentions to Copy types being valid for union fields
#94031
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…on-drop-suggest-copy-bound-alternative, r=davidtwco [diagnostics] Add mentions to `Copy` types being valid for `union` fields This came up from some user on Discord which was using a `T : PrimitiveInt` generic type, and they wanted to use in a `union`. Rather than adding a `Copy` bound, they started pondering about the `ManuallyDrop<T>` road, and how to correctly use `unsafe` to perform the drops. <img width="648" alt="Screen Shot 2022-02-15 at 22 28 34" src="https://user-images.githubusercontent.com/9920355/154152496-8f9be74b-ad59-4724-8f9e-48b446774e06.png"> - [Discord link](https://discord.com/channels/442252698964721669/443150878111694848/943092778534072320) So, it seemed like the error message for types with potential drop glue on `union` fields could be improved to also mention the `Copy` alternative, since in many cases where `union`s are concerned, people are dealing with PODs / `Copy` types anyways 🙂 ___ `@rustbot` modify labels: +A-diagnostics +D-terse
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…askrgr Rollup of 8 pull requests Successful merges: - rust-lang#89869 (Add documentation to more `From::from` implementations.) - rust-lang#93479 (Use `optflag` for `--report-time`) - rust-lang#93693 (Suggest deriving required supertraits) - rust-lang#93981 (Fix suggestion to slice if scurtinee is a reference to `Result` or `Option`) - rust-lang#93996 (Do not suggest "is a function" for free variables) - rust-lang#94030 (Correctly mark the span of captured arguments in `format_args!()`) - rust-lang#94031 ([diagnostics] Add mentions to `Copy` types being valid for `union` fields) - rust-lang#94064 (Update dist-x86_64-musl to Ubuntu 20.04) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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This came up from some user on Discord which was using a
T : PrimitiveIntgeneric type, and they wanted to use in aunion. Rather than adding aCopybound, they started pondering about theManuallyDrop<T>road, and how to correctly useunsafeto perform the drops.So, it seemed like the error message for types with potential drop glue on
unionfields could be improved to also mention theCopyalternative, since in many cases whereunions are concerned, people are dealing with PODs /Copytypes anyways 🙂@rustbot modify labels: +A-diagnostics +D-terse