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Document non-guarantees for Hash #90995

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Nov 27, 2021
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Document non-guarantees for Hash #90995

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Document non-guarantees for Hash
the8472 Nov 18, 2021
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the8472 Nov 23, 2021
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13 changes: 13 additions & 0 deletions library/core/src/hash/mod.rs
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Expand Up @@ -164,6 +164,19 @@ mod sip;
/// `0xFF` byte to the `Hasher` so that the values `("ab", "c")` and `("a",
/// "bc")` hash differently.
///
/// ## Portability
///
/// Due to differences in endianness and type sizes, data fed by `Hash` to a `Hasher`
/// should not be considered portable across platforms. Additionally the data passed by most
/// standard library types should not be considered stable between compiler versions.
///
/// This means tests shouldn't probe hard-coded hash values or data fed to a `Hasher` and
/// instead should check consistency with `Eq`.
///
/// Serialization formats intended to be portable between platforms or compiler versions should
/// either avoid encoding hashes or only rely on `Hash` and `Hasher` implementations that
/// provide additional guarantees.
///
/// [`HashMap`]: ../../std/collections/struct.HashMap.html
/// [`HashSet`]: ../../std/collections/struct.HashSet.html
/// [`hash`]: Hash::hash
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