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PartialEq: handle longer transitive chains

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This commit is contained in:
Ralf Jung 2023-11-20 21:55:17 +01:00
parent e1fadb2c35
commit a63880c4d3
1 changed files with 4 additions and 2 deletions
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6
library/core/src/cmp.rs
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@ -61,11 +61,13 @@ use self::Ordering::*;
/// The equality relation `==` must satisfy the following conditions
/// (for all `a`, `b`, `c` of type `A`, `B`, `C`):
///
/// - **Symmetric**: if `A: PartialEq<B>` and `B: PartialEq<A>`, then **`a == b`
/// - **Symmetry**: if `A: PartialEq<B>` and `B: PartialEq<A>`, then **`a == b`
/// implies `b == a`**; and
///
/// - **Transitive**: if `A: PartialEq<B>` and `B: PartialEq<C>` and `A:
/// - **Transitivity**: if `A: PartialEq<B>` and `B: PartialEq<C>` and `A:
/// PartialEq<C>`, then **`a == b` and `b == c` implies `a == c`**.
/// This must also work for longer chains, such as when `A: PartialEq<B>`, `B: PartialEq<C>`,
/// `C: PartialEq<D>`, and `A: PartialEq<D>` all exist.
///
/// Note that the `B: PartialEq<A>` (symmetric) and `A: PartialEq<C>`
/// (transitive) impls are not forced to exist, but these requirements apply