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Update thread local docs with idiomatic cell type use

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The `thread_local!` examples use `RefCell` for `Copy` types. Update
examples to have one `Copy` and one non-`Copy` type using `Cell` and
`RefCell`, respectively.
This commit is contained in:
Trevor Gross 2024-04-08 17:43:24 -04:00
parent 537aab7a2e
commit 2aec2fe3b8
1 changed files with 18 additions and 16 deletions
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34
library/std/src/thread/local.rs
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@ -53,25 +53,25 @@ use crate::fmt;
/// # Examples
///
/// ```
/// use std::cell::RefCell;
/// use std::cell::Cell;
/// use std::thread;
///
/// thread_local!(static FOO: RefCell<u32> = RefCell::new(1));
/// thread_local!(static FOO: Cell<u32> = Cell::new(1));
///
/// FOO.with_borrow(|v| assert_eq!(*v, 1));
/// FOO.with_borrow_mut(|v| *v = 2);
/// assert_eq!(FOO.get(), 1);
/// FOO.set(2);
///
/// // each thread starts out with the initial value of 1
/// let t = thread::spawn(move|| {
/// FOO.with_borrow(|v| assert_eq!(*v, 1));
/// FOO.with_borrow_mut(|v| *v = 3);
/// assert_eq!(FOO.get(), 1);
/// FOO.set(3);
/// });
///
/// // wait for the thread to complete and bail out on panic
/// t.join().unwrap();
///
/// // we retain our original value of 2 despite the child thread
/// FOO.with_borrow(|v| assert_eq!(*v, 2));
/// assert_eq!(FOO.get(), 2);
/// ```
///
/// # Platform-specific behavior
@ -141,15 +141,16 @@ impl<T: 'static> fmt::Debug for LocalKey<T> {
/// Publicity and attributes for each static are allowed. Example:
///
/// ```
/// use std::cell::RefCell;
/// thread_local! {
/// pub static FOO: RefCell<u32> = RefCell::new(1);
/// use std::cell::{Cell, RefCell};
///
/// static BAR: RefCell<f32> = RefCell::new(1.0);
/// thread_local! {
/// pub static FOO: Cell<u32> = Cell::new(1);
///
/// static BAR: RefCell<Vec<f32>> = RefCell::new(vec![1.0, 2.0]);
/// }
///
/// FOO.with_borrow(|v| assert_eq!(*v, 1));
/// BAR.with_borrow(|v| assert_eq!(*v, 1.0));
/// assert_eq!(FOO.get(), 1);
/// BAR.with_borrow(|v| assert_eq!(v[1], 2.0));
/// ```
///
/// Note that only shared references (`&T`) to the inner data may be obtained, so a
@ -164,12 +165,13 @@ impl<T: 'static> fmt::Debug for LocalKey<T> {
/// track any additional state.
///
/// ```
/// use std::cell::Cell;
/// use std::cell::RefCell;
///
/// thread_local! {
/// pub static FOO: Cell<u32> = const { Cell::new(1) };
/// pub static FOO: RefCell<Vec<u32>> = const { RefCell::new(Vec::new()) };
/// }
///
/// assert_eq!(FOO.get(), 1);
/// FOO.with_borrow(|v| assert_eq!(v.len(), 0));
/// ```
///
/// See [`LocalKey` documentation][`std::thread::LocalKey`] for more