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constified str::from_utf8_unchecked_mut #86804

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constified str::from_utf8_unchecked_mut #86804

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12 changes: 6 additions & 6 deletions library/core/src/str/converts.rs
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Expand Up @@ -183,10 +183,10 @@ pub const unsafe fn from_utf8_unchecked(v: &[u8]) -> &str {
/// ```
#[inline]
#[stable(feature = "str_mut_extras", since = "1.20.0")]
pub unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str {
// SAFETY: the caller must guarantee that the bytes `v`
// are valid UTF-8, thus the cast to `*mut str` is safe.
// Also, the pointer dereference is safe because that pointer
// comes from a reference which is guaranteed to be valid for writes.
unsafe { &mut *(v as *mut [u8] as *mut str) }
#[rustc_const_stable(feature = "const_str_from_utf8_unchecked", since = "1.55.0")]
#[rustc_allow_const_fn_unstable(const_fn_transmute)]
pub const unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str {
// SAFETY: the caller must guarantee that the bytes `v` are valid UTF-8.
// Also relies on `&mut str` and `&mut [u8]` having the same layout.
unsafe { mem::transmute(v) }
}