mirror of
https://github.com/rust-lang/rust.git
synced 2024-12-11 16:15:03 +00:00
3cddc8bff6
The signature for new was ``` fn new<F>(f: F) -> Lazy<T, F> ``` Notably, with `F` unconstrained, `T` can be literally anything, and just `let _ = Lazy::new(|| 92)` would not typecheck. This historiacally was a necessity -- `new` is a `const` function, it couldn't have any bounds. Today though, we can move `new` under the `F: FnOnce() -> T` bound, which gives the compiler enough data to infer the type of T from closure.
145 lines
3.3 KiB
Rust
145 lines
3.3 KiB
Rust
use core::{
|
|
cell::{Cell, LazyCell, OnceCell},
|
|
sync::atomic::{AtomicUsize, Ordering::SeqCst},
|
|
};
|
|
|
|
#[test]
|
|
fn once_cell() {
|
|
let c = OnceCell::new();
|
|
assert!(c.get().is_none());
|
|
c.get_or_init(|| 92);
|
|
assert_eq!(c.get(), Some(&92));
|
|
|
|
c.get_or_init(|| panic!("Kabom!"));
|
|
assert_eq!(c.get(), Some(&92));
|
|
}
|
|
|
|
#[test]
|
|
fn once_cell_get_mut() {
|
|
let mut c = OnceCell::new();
|
|
assert!(c.get_mut().is_none());
|
|
c.set(90).unwrap();
|
|
*c.get_mut().unwrap() += 2;
|
|
assert_eq!(c.get_mut(), Some(&mut 92));
|
|
}
|
|
|
|
#[test]
|
|
fn once_cell_drop() {
|
|
static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
|
|
struct Dropper;
|
|
impl Drop for Dropper {
|
|
fn drop(&mut self) {
|
|
DROP_CNT.fetch_add(1, SeqCst);
|
|
}
|
|
}
|
|
|
|
let x = OnceCell::new();
|
|
x.get_or_init(|| Dropper);
|
|
assert_eq!(DROP_CNT.load(SeqCst), 0);
|
|
drop(x);
|
|
assert_eq!(DROP_CNT.load(SeqCst), 1);
|
|
}
|
|
|
|
#[test]
|
|
fn unsync_once_cell_drop_empty() {
|
|
let x = OnceCell::<&'static str>::new();
|
|
drop(x);
|
|
}
|
|
|
|
#[test]
|
|
const fn once_cell_const() {
|
|
let _once_cell: OnceCell<u32> = OnceCell::new();
|
|
let _once_cell: OnceCell<u32> = OnceCell::from(32);
|
|
}
|
|
|
|
#[test]
|
|
fn clone() {
|
|
let s = OnceCell::new();
|
|
let c = s.clone();
|
|
assert!(c.get().is_none());
|
|
|
|
s.set("hello").unwrap();
|
|
let c = s.clone();
|
|
assert_eq!(c.get().map(|c| *c), Some("hello"));
|
|
}
|
|
|
|
#[test]
|
|
fn from_impl() {
|
|
assert_eq!(OnceCell::from("value").get(), Some(&"value"));
|
|
assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
|
|
}
|
|
|
|
#[test]
|
|
fn partialeq_impl() {
|
|
assert!(OnceCell::from("value") == OnceCell::from("value"));
|
|
assert!(OnceCell::from("foo") != OnceCell::from("bar"));
|
|
|
|
assert!(OnceCell::<&'static str>::new() == OnceCell::new());
|
|
assert!(OnceCell::<&'static str>::new() != OnceCell::from("value"));
|
|
}
|
|
|
|
#[test]
|
|
fn into_inner() {
|
|
let cell: OnceCell<&'static str> = OnceCell::new();
|
|
assert_eq!(cell.into_inner(), None);
|
|
let cell = OnceCell::new();
|
|
cell.set("hello").unwrap();
|
|
assert_eq!(cell.into_inner(), Some("hello"));
|
|
}
|
|
|
|
#[test]
|
|
fn lazy_new() {
|
|
let called = Cell::new(0);
|
|
let x = LazyCell::new(|| {
|
|
called.set(called.get() + 1);
|
|
92
|
|
});
|
|
|
|
assert_eq!(called.get(), 0);
|
|
|
|
let y = *x - 30;
|
|
assert_eq!(y, 62);
|
|
assert_eq!(called.get(), 1);
|
|
|
|
let y = *x - 30;
|
|
assert_eq!(y, 62);
|
|
assert_eq!(called.get(), 1);
|
|
}
|
|
|
|
// Check that we can infer `T` from closure's type.
|
|
#[test]
|
|
fn lazy_type_inference() {
|
|
let _ = LazyCell::new(|| ());
|
|
}
|
|
|
|
#[test]
|
|
fn aliasing_in_get() {
|
|
let x = OnceCell::new();
|
|
x.set(42).unwrap();
|
|
let at_x = x.get().unwrap(); // --- (shared) borrow of inner `Option<T>` --+
|
|
let _ = x.set(27); // <-- temporary (unique) borrow of inner `Option<T>` |
|
|
println!("{at_x}"); // <------- up until here ---------------------------+
|
|
}
|
|
|
|
#[test]
|
|
#[should_panic(expected = "reentrant init")]
|
|
fn reentrant_init() {
|
|
let x: OnceCell<Box<i32>> = OnceCell::new();
|
|
let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
|
|
x.get_or_init(|| {
|
|
let r = x.get_or_init(|| Box::new(92));
|
|
dangling_ref.set(Some(r));
|
|
Box::new(62)
|
|
});
|
|
eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
|
|
}
|
|
|
|
#[test]
|
|
fn dropck() {
|
|
let cell = OnceCell::new();
|
|
{
|
|
let s = String::new();
|
|
cell.set(&s).unwrap();
|
|
}
|
|
}
|