Rollup merge of rust-lang#103280 - finnbear:impl_string_leak_2, r=jos…

…htriplett

(rust-lang#102929) Implement `String::leak` (attempt 2)

Implementation of `String::leak` (rust-lang#102929)

ACP: rust-lang/libs-team#109

Supersedes rust-lang#102941 (see previous reviews there)

`@rustbot` label +T-libs-api -T-libs

library/alloc/src/string.rs

@@ -67,7 +67,7 @@ use core::str::Utf8Chunks;
 use crate::borrow::{Cow, ToOwned};
 use crate::boxed::Box;
 use crate::collections::TryReserveError;
-use crate::str::{self, Chars, Utf8Error};
+use crate::str::{self, from_utf8_unchecked_mut, Chars, Utf8Error};
 #[cfg(not(no_global_oom_handling))]
 use crate::str::{from_boxed_utf8_unchecked, FromStr};
 use crate::vec::Vec;
@@ -1849,6 +1849,35 @@ impl String {
  let slice = self.vec.into_boxed_slice();
  unsafe { from_boxed_utf8_unchecked(slice) }
  }
+
+ /// Consumes and leaks the `String`, returning a mutable reference to the contents,
+ /// `&'a mut str`.
+ ///
+ /// This is mainly useful for data that lives for the remainder of
+ /// the program's life. Dropping the returned reference will cause a memory
+ /// leak.
+ ///
+ /// It does not reallocate or shrink the `String`,
+ /// so the leaked allocation may include unused capacity that is not part
+ /// of the returned slice.
+ ///
+ /// # Examples
+ ///
+ /// Simple usage:
+ ///
+ /// ```
+ /// #![feature(string_leak)]
+ ///
+ /// let x = String::from("bucket");
+ /// let static_ref: &'static mut str = x.leak();
+ /// assert_eq!(static_ref, "bucket");
+ /// ```
+ #[unstable(feature = "string_leak", issue = "102929")]
+ #[inline]
+ pub fn leak(self) -> &'static mut str {
+ let slice = self.vec.leak();
+ unsafe { from_utf8_unchecked_mut(slice) }
+ }
 }
 
 impl FromUtf8Error {