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Add Derive not possible question to Copy #35042

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Aug 5, 2016
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Add Derive not possible question to Copy #35042

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6 changes: 6 additions & 0 deletions src/libcore/marker.rs
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Expand Up @@ -144,6 +144,12 @@ pub trait Unsize<T: ?Sized> {
/// Generalizing the latter case, any type implementing `Drop` can't be `Copy`, because it's
/// managing some resource besides its own `size_of::<T>()` bytes.
///
/// ## What if I derive `Copy` on a type that can't?
///
/// If you try to derive `Copy` on a struct or enum, you will get a compile-time error.
/// Specifically, with structs you'll get [E0204](https://doc.rust-lang.org/error-index.html#E0204)
/// and with enums you'll get [E0205](https://doc.rust-lang.org/error-index.html#E0205).
///
/// ## When should my type be `Copy`?
///
/// Generally speaking, if your type _can_ implement `Copy`, it should. There's one important thing
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