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7b97a5ca84
Emit explanatory note for move errors in packed struct derives Derive expansions for packed structs with non-`Copy` fields cause move errors because they prefer copying over borrowing since borrowing the fields of a packed struct can result in unaligned access. This underlying cause of the errors, however, is not apparent to the user. This PR adds a diagnostic note to make it clear to the user (the new note is on the second last line): ``` tests/ui/derives/deriving-with-repr-packed-move-errors.rs:13:16 | 12 | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)] | ----- in this derive macro expansion 13 | struct StructA(String); | ^^^^^^ move occurs because `self.0` has type `String`, which does not implement the `Copy` trait | = note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour = note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info) ``` Fixes #117406 Partially addresses #110777 |
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| COMPILER_TESTS.md | ||