diff --git a/library/core/src/option.rs b/library/core/src/option.rs index ff48575e2c06f..7b55093694217 100644 --- a/library/core/src/option.rs +++ b/library/core/src/option.rs @@ -120,20 +120,22 @@ //! //! Rust guarantees to optimize the following types `T` such that //! [`Option`] has the same size, alignment, and [function call ABI] as `T`. In some -//! of these cases, Rust further guarantees that -//! `transmute::<_, Option>([0u8; size_of::()])` is sound and -//! produces `Option::::None`. These cases are identified by the -//! second column: -//! -//! | `T` | `transmute::<_, Option>([0u8; size_of::()])` sound? | -//! |---------------------------------------------------------------------|----------------------------------------------------------------------| -//! | [`Box`] (specifically, only `Box`) | when `U: Sized` | -//! | `&U` | when `U: Sized` | -//! | `&mut U` | when `U: Sized` | -//! | `fn`, `extern "C" fn`[^extern_fn] | always | -//! | [`num::NonZero*`] | always | -//! | [`ptr::NonNull`] | when `U: Sized` | -//! | `#[repr(transparent)]` struct around one of the types in this list. | when it holds for the inner type | +//! of these cases, Rust further guarantees the following: +//! - `transmute::<_, Option>([0u8; size_of::()])` is sound and produces +//! `Option::::None` +//! - `transmute::<_, [u8; size_of::()]>(Option::::None)` is sound and produces +//! `[0u8; size_of::()]` +//! These cases are identified by the second column: +//! +//! | `T` | Transmuting between `[0u8; size_of::()]` and `Option::::None` sound? | +//! |---------------------------------------------------------------------|----------------------------------------------------------------------------| +//! | [`Box`] (specifically, only `Box`) | when `U: Sized` | +//! | `&U` | when `U: Sized` | +//! | `&mut U` | when `U: Sized` | +//! | `fn`, `extern "C" fn`[^extern_fn] | always | +//! | [`num::NonZero*`] | always | +//! | [`ptr::NonNull`] | when `U: Sized` | +//! | `#[repr(transparent)]` struct around one of the types in this list. | when it holds for the inner type | //! //! [^extern_fn]: this remains true for any argument/return types and any other ABI: `extern "abi" fn` (_e.g._, `extern "system" fn`) //!