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| author | Michael Krasnitski <michael.krasnitski@gmail.com> | 2023-03-13 01:31:02 -0400 |
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| committer | Michael Krasnitski <michael.krasnitski@gmail.com> | 2023-03-13 01:31:02 -0400 |
| commit | 571b0fef01ea994cd9a81405283049b5595499c5 (patch) | |
| tree | 5b92a697fb6f0dceb82fefedb9c89e8d648ee915 /library/core/src | |
| parent | b05bb2900825e4d063ebf3f0f11afb08baed3bc6 (diff) | |
| download | rust-571b0fef01ea994cd9a81405283049b5595499c5.tar.gz rust-571b0fef01ea994cd9a81405283049b5595499c5.zip | |
Clarify stability guarantee for lifetimes in enum discriminants
Diffstat (limited to 'library/core/src')
| -rw-r--r-- | library/core/src/mem/mod.rs | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/library/core/src/mem/mod.rs b/library/core/src/mem/mod.rs index a67df7ed557..aa53aa29bdb 100644 --- a/library/core/src/mem/mod.rs +++ b/library/core/src/mem/mod.rs @@ -1118,6 +1118,11 @@ impl<T> fmt::Debug for Discriminant<T> { /// /// [Reference]: ../../reference/items/enumerations.html#custom-discriminant-values-for-fieldless-enumerations /// +/// The value of a [`Discriminant<T>`] is independent of any *lifetimes* in `T`. As such, reading +/// or writing a `Discriminant<Foo<'a>>` as a `Discriminant<Foo<'b>>` (whether via [`transmute`] or +/// otherwise) is always sound. Note that this is **not** true for other kinds of generic +/// parameters; `Discriminant<Foo<A>>` and `Discriminant<Foo<B>>` might be incompatible. +/// /// # Examples /// /// This can be used to compare enums that carry data, while disregarding |