mirror of
https://github.com/rust-lang/rust
synced 2024-10-18 22:43:56 +00:00
Move/rename lazy::{OnceCell, Lazy}
to cell::{OnceCell, LazyCell}
This commit is contained in:
parent
392d272868
commit
7c360dc117
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@ -36,9 +36,9 @@
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use libc::c_uint;
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use smallvec::SmallVec;
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use std::cell::OnceCell;
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use std::cell::RefCell;
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use std::iter;
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use std::lazy::OnceCell;
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use tracing::debug;
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mod create_scope_map;
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@ -38,11 +38,11 @@
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use tempfile::Builder as TempFileBuilder;
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use std::borrow::Borrow;
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use std::cell::OnceCell;
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use std::collections::BTreeSet;
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use std::ffi::OsString;
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use std::fs::{File, OpenOptions};
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use std::io::{BufWriter, Write};
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use std::lazy::OnceCell;
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use std::ops::Deref;
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use std::path::{Path, PathBuf};
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use std::process::{ExitStatus, Output, Stdio};
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@ -173,7 +173,7 @@ pub fn par_for_each_in<T: IntoIterator>(t: T, for_each: impl Fn(T::Item) + Sync
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pub use std::cell::RefMut as LockGuard;
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pub use std::cell::RefMut as MappedLockGuard;
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pub use std::lazy::OnceCell;
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pub use std::cell::OnceCell;
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use std::cell::RefCell as InnerRwLock;
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use std::cell::RefCell as InnerLock;
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@ -18,7 +18,7 @@
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use tracing::{instrument, trace};
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#[cfg(not(parallel_compiler))]
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use std::lazy::Lazy;
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use std::cell::LazyCell as Lazy;
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#[cfg(parallel_compiler)]
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use std::lazy::SyncLazy as Lazy;
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@ -29,9 +29,9 @@
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use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
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use rustc_trait_selection::traits::{self, ObligationCause, ObligationCauseCode, WellFormedLoc};
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use std::cell::LazyCell;
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use std::convert::TryInto;
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use std::iter;
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use std::lazy::Lazy;
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use std::ops::ControlFlow;
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/// Helper type of a temporary returned by `.for_item(...)`.
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@ -1728,7 +1728,7 @@ fn check_variances_for_type_defn<'tcx>(
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identify_constrained_generic_params(tcx, ty_predicates, None, &mut constrained_parameters);
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// Lazily calculated because it is only needed in case of an error.
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let explicitly_bounded_params = Lazy::new(|| {
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let explicitly_bounded_params = LazyCell::new(|| {
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let icx = crate::collect::ItemCtxt::new(tcx, item.def_id.to_def_id());
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hir_generics
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.predicates
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@ -199,6 +199,14 @@
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use crate::ops::{CoerceUnsized, Deref, DerefMut};
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use crate::ptr::{self, NonNull};
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mod lazy;
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mod once;
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#[unstable(feature = "once_cell", issue = "74465")]
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pub use lazy::LazyCell;
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#[unstable(feature = "once_cell", issue = "74465")]
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pub use once::OnceCell;
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/// A mutable memory location.
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///
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/// # Examples
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104
library/core/src/cell/lazy.rs
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104
library/core/src/cell/lazy.rs
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@ -0,0 +1,104 @@
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use crate::cell::{Cell, OnceCell};
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use crate::fmt;
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use crate::ops::Deref;
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/// A value which is initialized on the first access.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::LazyCell;
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///
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/// let lazy: LazyCell<i32> = LazyCell::new(|| {
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/// println!("initializing");
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/// 92
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/// });
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/// println!("ready");
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/// println!("{}", *lazy);
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/// println!("{}", *lazy);
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///
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/// // Prints:
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/// // ready
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/// // initializing
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/// // 92
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/// // 92
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub struct LazyCell<T, F = fn() -> T> {
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cell: OnceCell<T>,
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init: Cell<Option<F>>,
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}
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impl<T, F> LazyCell<T, F> {
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/// Creates a new lazy value with the given initializing function.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::LazyCell;
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///
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/// let hello = "Hello, World!".to_string();
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///
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/// let lazy = LazyCell::new(|| hello.to_uppercase());
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///
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/// assert_eq!(&*lazy, "HELLO, WORLD!");
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub const fn new(init: F) -> LazyCell<T, F> {
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LazyCell { cell: OnceCell::new(), init: Cell::new(Some(init)) }
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}
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}
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impl<T, F: FnOnce() -> T> LazyCell<T, F> {
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/// Forces the evaluation of this lazy value and returns a reference to
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/// the result.
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///
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/// This is equivalent to the `Deref` impl, but is explicit.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::LazyCell;
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///
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/// let lazy = LazyCell::new(|| 92);
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///
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/// assert_eq!(LazyCell::force(&lazy), &92);
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/// assert_eq!(&*lazy, &92);
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub fn force(this: &LazyCell<T, F>) -> &T {
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this.cell.get_or_init(|| match this.init.take() {
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Some(f) => f(),
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None => panic!("`Lazy` instance has previously been poisoned"),
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})
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}
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}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T, F: FnOnce() -> T> Deref for LazyCell<T, F> {
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type Target = T;
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fn deref(&self) -> &T {
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LazyCell::force(self)
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}
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}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T: Default> Default for LazyCell<T> {
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/// Creates a new lazy value using `Default` as the initializing function.
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fn default() -> LazyCell<T> {
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LazyCell::new(T::default)
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}
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}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T: fmt::Debug, F> fmt::Debug for LazyCell<T, F> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("Lazy").field("cell", &self.cell).field("init", &"..").finish()
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}
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}
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283
library/core/src/cell/once.rs
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283
library/core/src/cell/once.rs
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use crate::cell::UnsafeCell;
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use crate::fmt;
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use crate::mem;
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/// A cell which can be written to only once.
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///
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/// Unlike `RefCell`, a `OnceCell` only provides shared `&T` references to its value.
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/// Unlike `Cell`, a `OnceCell` doesn't require copying or replacing the value to access it.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::OnceCell;
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///
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/// let cell = OnceCell::new();
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/// assert!(cell.get().is_none());
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///
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/// let value: &String = cell.get_or_init(|| {
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/// "Hello, World!".to_string()
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/// });
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/// assert_eq!(value, "Hello, World!");
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/// assert!(cell.get().is_some());
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub struct OnceCell<T> {
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// Invariant: written to at most once.
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inner: UnsafeCell<Option<T>>,
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}
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impl<T> OnceCell<T> {
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/// Creates a new empty cell.
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#[unstable(feature = "once_cell", issue = "74465")]
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#[must_use]
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pub const fn new() -> OnceCell<T> {
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OnceCell { inner: UnsafeCell::new(None) }
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}
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/// Gets the reference to the underlying value.
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///
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/// Returns `None` if the cell is empty.
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#[unstable(feature = "once_cell", issue = "74465")]
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pub fn get(&self) -> Option<&T> {
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// SAFETY: Safe due to `inner`'s invariant
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unsafe { &*self.inner.get() }.as_ref()
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}
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/// Gets the mutable reference to the underlying value.
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///
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/// Returns `None` if the cell is empty.
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#[unstable(feature = "once_cell", issue = "74465")]
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pub fn get_mut(&mut self) -> Option<&mut T> {
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self.inner.get_mut().as_mut()
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}
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/// Sets the contents of the cell to `value`.
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///
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/// # Errors
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///
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/// This method returns `Ok(())` if the cell was empty and `Err(value)` if
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/// it was full.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::OnceCell;
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///
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/// let cell = OnceCell::new();
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/// assert!(cell.get().is_none());
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///
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/// assert_eq!(cell.set(92), Ok(()));
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/// assert_eq!(cell.set(62), Err(62));
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///
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/// assert!(cell.get().is_some());
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub fn set(&self, value: T) -> Result<(), T> {
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// SAFETY: Safe because we cannot have overlapping mutable borrows
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let slot = unsafe { &*self.inner.get() };
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if slot.is_some() {
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return Err(value);
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}
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// SAFETY: This is the only place where we set the slot, no races
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// due to reentrancy/concurrency are possible, and we've
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// checked that slot is currently `None`, so this write
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// maintains the `inner`'s invariant.
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let slot = unsafe { &mut *self.inner.get() };
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*slot = Some(value);
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Ok(())
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}
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/// Gets the contents of the cell, initializing it with `f`
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/// if the cell was empty.
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///
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/// # Panics
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///
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/// If `f` panics, the panic is propagated to the caller, and the cell
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/// remains uninitialized.
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///
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/// It is an error to reentrantly initialize the cell from `f`. Doing
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/// so results in a panic.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::OnceCell;
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///
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/// let cell = OnceCell::new();
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/// let value = cell.get_or_init(|| 92);
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/// assert_eq!(value, &92);
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/// let value = cell.get_or_init(|| unreachable!());
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/// assert_eq!(value, &92);
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub fn get_or_init<F>(&self, f: F) -> &T
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where
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F: FnOnce() -> T,
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{
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match self.get_or_try_init(|| Ok::<T, !>(f())) {
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Ok(val) => val,
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}
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}
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/// Gets the contents of the cell, initializing it with `f` if
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/// the cell was empty. If the cell was empty and `f` failed, an
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/// error is returned.
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///
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/// # Panics
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///
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/// If `f` panics, the panic is propagated to the caller, and the cell
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/// remains uninitialized.
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///
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/// It is an error to reentrantly initialize the cell from `f`. Doing
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/// so results in a panic.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::OnceCell;
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///
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/// let cell = OnceCell::new();
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/// assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
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/// assert!(cell.get().is_none());
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/// let value = cell.get_or_try_init(|| -> Result<i32, ()> {
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/// Ok(92)
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/// });
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/// assert_eq!(value, Ok(&92));
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/// assert_eq!(cell.get(), Some(&92))
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E>
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where
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F: FnOnce() -> Result<T, E>,
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{
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if let Some(val) = self.get() {
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return Ok(val);
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}
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/// Avoid inlining the initialization closure into the common path that fetches
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/// the already initialized value
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#[cold]
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fn outlined_call<F, T, E>(f: F) -> Result<T, E>
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where
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F: FnOnce() -> Result<T, E>,
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{
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f()
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}
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let val = outlined_call(f)?;
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// Note that *some* forms of reentrant initialization might lead to
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// UB (see `reentrant_init` test). I believe that just removing this
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// `assert`, while keeping `set/get` would be sound, but it seems
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// better to panic, rather than to silently use an old value.
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assert!(self.set(val).is_ok(), "reentrant init");
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Ok(self.get().unwrap())
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}
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/// Consumes the cell, returning the wrapped value.
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///
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/// Returns `None` if the cell was empty.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::OnceCell;
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///
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/// let cell: OnceCell<String> = OnceCell::new();
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/// assert_eq!(cell.into_inner(), None);
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///
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/// let cell = OnceCell::new();
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/// cell.set("hello".to_string()).unwrap();
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/// assert_eq!(cell.into_inner(), Some("hello".to_string()));
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub fn into_inner(self) -> Option<T> {
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// Because `into_inner` takes `self` by value, the compiler statically verifies
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// that it is not currently borrowed. So it is safe to move out `Option<T>`.
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self.inner.into_inner()
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}
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/// Takes the value out of this `OnceCell`, moving it back to an uninitialized state.
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///
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/// Has no effect and returns `None` if the `OnceCell` hasn't been initialized.
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///
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/// Safety is guaranteed by requiring a mutable reference.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(once_cell)]
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///
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/// use std::cell::OnceCell;
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///
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/// let mut cell: OnceCell<String> = OnceCell::new();
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/// assert_eq!(cell.take(), None);
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///
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/// let mut cell = OnceCell::new();
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/// cell.set("hello".to_string()).unwrap();
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/// assert_eq!(cell.take(), Some("hello".to_string()));
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/// assert_eq!(cell.get(), None);
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/// ```
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#[unstable(feature = "once_cell", issue = "74465")]
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pub fn take(&mut self) -> Option<T> {
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mem::take(self).into_inner()
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}
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}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T> Default for OnceCell<T> {
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fn default() -> Self {
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Self::new()
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}
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}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T: fmt::Debug> fmt::Debug for OnceCell<T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self.get() {
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Some(v) => f.debug_tuple("OnceCell").field(v).finish(),
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None => f.write_str("OnceCell(Uninit)"),
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}
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}
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}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T: Clone> Clone for OnceCell<T> {
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fn clone(&self) -> OnceCell<T> {
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let res = OnceCell::new();
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if let Some(value) = self.get() {
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match res.set(value.clone()) {
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Ok(()) => (),
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Err(_) => unreachable!(),
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}
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}
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res
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}
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}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T: PartialEq> PartialEq for OnceCell<T> {
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fn eq(&self, other: &Self) -> bool {
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self.get() == other.get()
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}
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}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T: Eq> Eq for OnceCell<T> {}
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#[unstable(feature = "once_cell", issue = "74465")]
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impl<T> const From<T> for OnceCell<T> {
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/// Creates a new `OnceCell<T>` which already contains the given `value`.
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fn from(value: T) -> Self {
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OnceCell { inner: UnsafeCell::new(Some(value)) }
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||||
}
|
||||
}
|
|
@ -1,389 +1 @@
|
|||
//! Lazy values and one-time initialization of static data.
|
||||
|
||||
use crate::cell::{Cell, UnsafeCell};
|
||||
use crate::fmt;
|
||||
use crate::mem;
|
||||
use crate::ops::Deref;
|
||||
|
||||
/// A cell which can be written to only once.
|
||||
///
|
||||
/// Unlike `RefCell`, a `OnceCell` only provides shared `&T` references to its value.
|
||||
/// Unlike `Cell`, a `OnceCell` doesn't require copying or replacing the value to access it.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// use std::lazy::OnceCell;
|
||||
///
|
||||
/// let cell = OnceCell::new();
|
||||
/// assert!(cell.get().is_none());
|
||||
///
|
||||
/// let value: &String = cell.get_or_init(|| {
|
||||
/// "Hello, World!".to_string()
|
||||
/// });
|
||||
/// assert_eq!(value, "Hello, World!");
|
||||
/// assert!(cell.get().is_some());
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub struct OnceCell<T> {
|
||||
// Invariant: written to at most once.
|
||||
inner: UnsafeCell<Option<T>>,
|
||||
}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T> Default for OnceCell<T> {
|
||||
fn default() -> Self {
|
||||
Self::new()
|
||||
}
|
||||
}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T: fmt::Debug> fmt::Debug for OnceCell<T> {
|
||||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||||
match self.get() {
|
||||
Some(v) => f.debug_tuple("OnceCell").field(v).finish(),
|
||||
None => f.write_str("OnceCell(Uninit)"),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T: Clone> Clone for OnceCell<T> {
|
||||
fn clone(&self) -> OnceCell<T> {
|
||||
let res = OnceCell::new();
|
||||
if let Some(value) = self.get() {
|
||||
match res.set(value.clone()) {
|
||||
Ok(()) => (),
|
||||
Err(_) => unreachable!(),
|
||||
}
|
||||
}
|
||||
res
|
||||
}
|
||||
}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T: PartialEq> PartialEq for OnceCell<T> {
|
||||
fn eq(&self, other: &Self) -> bool {
|
||||
self.get() == other.get()
|
||||
}
|
||||
}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T: Eq> Eq for OnceCell<T> {}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T> const From<T> for OnceCell<T> {
|
||||
/// Creates a new `OnceCell<T>` which already contains the given `value`.
|
||||
fn from(value: T) -> Self {
|
||||
OnceCell { inner: UnsafeCell::new(Some(value)) }
|
||||
}
|
||||
}
|
||||
|
||||
impl<T> OnceCell<T> {
|
||||
/// Creates a new empty cell.
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
#[must_use]
|
||||
pub const fn new() -> OnceCell<T> {
|
||||
OnceCell { inner: UnsafeCell::new(None) }
|
||||
}
|
||||
|
||||
/// Gets the reference to the underlying value.
|
||||
///
|
||||
/// Returns `None` if the cell is empty.
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub fn get(&self) -> Option<&T> {
|
||||
// SAFETY: Safe due to `inner`'s invariant
|
||||
unsafe { &*self.inner.get() }.as_ref()
|
||||
}
|
||||
|
||||
/// Gets the mutable reference to the underlying value.
|
||||
///
|
||||
/// Returns `None` if the cell is empty.
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub fn get_mut(&mut self) -> Option<&mut T> {
|
||||
self.inner.get_mut().as_mut()
|
||||
}
|
||||
|
||||
/// Sets the contents of the cell to `value`.
|
||||
///
|
||||
/// # Errors
|
||||
///
|
||||
/// This method returns `Ok(())` if the cell was empty and `Err(value)` if
|
||||
/// it was full.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// use std::lazy::OnceCell;
|
||||
///
|
||||
/// let cell = OnceCell::new();
|
||||
/// assert!(cell.get().is_none());
|
||||
///
|
||||
/// assert_eq!(cell.set(92), Ok(()));
|
||||
/// assert_eq!(cell.set(62), Err(62));
|
||||
///
|
||||
/// assert!(cell.get().is_some());
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub fn set(&self, value: T) -> Result<(), T> {
|
||||
// SAFETY: Safe because we cannot have overlapping mutable borrows
|
||||
let slot = unsafe { &*self.inner.get() };
|
||||
if slot.is_some() {
|
||||
return Err(value);
|
||||
}
|
||||
|
||||
// SAFETY: This is the only place where we set the slot, no races
|
||||
// due to reentrancy/concurrency are possible, and we've
|
||||
// checked that slot is currently `None`, so this write
|
||||
// maintains the `inner`'s invariant.
|
||||
let slot = unsafe { &mut *self.inner.get() };
|
||||
*slot = Some(value);
|
||||
Ok(())
|
||||
}
|
||||
|
||||
/// Gets the contents of the cell, initializing it with `f`
|
||||
/// if the cell was empty.
|
||||
///
|
||||
/// # Panics
|
||||
///
|
||||
/// If `f` panics, the panic is propagated to the caller, and the cell
|
||||
/// remains uninitialized.
|
||||
///
|
||||
/// It is an error to reentrantly initialize the cell from `f`. Doing
|
||||
/// so results in a panic.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// use std::lazy::OnceCell;
|
||||
///
|
||||
/// let cell = OnceCell::new();
|
||||
/// let value = cell.get_or_init(|| 92);
|
||||
/// assert_eq!(value, &92);
|
||||
/// let value = cell.get_or_init(|| unreachable!());
|
||||
/// assert_eq!(value, &92);
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub fn get_or_init<F>(&self, f: F) -> &T
|
||||
where
|
||||
F: FnOnce() -> T,
|
||||
{
|
||||
match self.get_or_try_init(|| Ok::<T, !>(f())) {
|
||||
Ok(val) => val,
|
||||
}
|
||||
}
|
||||
|
||||
/// Gets the contents of the cell, initializing it with `f` if
|
||||
/// the cell was empty. If the cell was empty and `f` failed, an
|
||||
/// error is returned.
|
||||
///
|
||||
/// # Panics
|
||||
///
|
||||
/// If `f` panics, the panic is propagated to the caller, and the cell
|
||||
/// remains uninitialized.
|
||||
///
|
||||
/// It is an error to reentrantly initialize the cell from `f`. Doing
|
||||
/// so results in a panic.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// use std::lazy::OnceCell;
|
||||
///
|
||||
/// let cell = OnceCell::new();
|
||||
/// assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
|
||||
/// assert!(cell.get().is_none());
|
||||
/// let value = cell.get_or_try_init(|| -> Result<i32, ()> {
|
||||
/// Ok(92)
|
||||
/// });
|
||||
/// assert_eq!(value, Ok(&92));
|
||||
/// assert_eq!(cell.get(), Some(&92))
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E>
|
||||
where
|
||||
F: FnOnce() -> Result<T, E>,
|
||||
{
|
||||
if let Some(val) = self.get() {
|
||||
return Ok(val);
|
||||
}
|
||||
/// Avoid inlining the initialization closure into the common path that fetches
|
||||
/// the already initialized value
|
||||
#[cold]
|
||||
fn outlined_call<F, T, E>(f: F) -> Result<T, E>
|
||||
where
|
||||
F: FnOnce() -> Result<T, E>,
|
||||
{
|
||||
f()
|
||||
}
|
||||
let val = outlined_call(f)?;
|
||||
// Note that *some* forms of reentrant initialization might lead to
|
||||
// UB (see `reentrant_init` test). I believe that just removing this
|
||||
// `assert`, while keeping `set/get` would be sound, but it seems
|
||||
// better to panic, rather than to silently use an old value.
|
||||
assert!(self.set(val).is_ok(), "reentrant init");
|
||||
Ok(self.get().unwrap())
|
||||
}
|
||||
|
||||
/// Consumes the cell, returning the wrapped value.
|
||||
///
|
||||
/// Returns `None` if the cell was empty.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// use std::lazy::OnceCell;
|
||||
///
|
||||
/// let cell: OnceCell<String> = OnceCell::new();
|
||||
/// assert_eq!(cell.into_inner(), None);
|
||||
///
|
||||
/// let cell = OnceCell::new();
|
||||
/// cell.set("hello".to_string()).unwrap();
|
||||
/// assert_eq!(cell.into_inner(), Some("hello".to_string()));
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub fn into_inner(self) -> Option<T> {
|
||||
// Because `into_inner` takes `self` by value, the compiler statically verifies
|
||||
// that it is not currently borrowed. So it is safe to move out `Option<T>`.
|
||||
self.inner.into_inner()
|
||||
}
|
||||
|
||||
/// Takes the value out of this `OnceCell`, moving it back to an uninitialized state.
|
||||
///
|
||||
/// Has no effect and returns `None` if the `OnceCell` hasn't been initialized.
|
||||
///
|
||||
/// Safety is guaranteed by requiring a mutable reference.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// use std::lazy::OnceCell;
|
||||
///
|
||||
/// let mut cell: OnceCell<String> = OnceCell::new();
|
||||
/// assert_eq!(cell.take(), None);
|
||||
///
|
||||
/// let mut cell = OnceCell::new();
|
||||
/// cell.set("hello".to_string()).unwrap();
|
||||
/// assert_eq!(cell.take(), Some("hello".to_string()));
|
||||
/// assert_eq!(cell.get(), None);
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub fn take(&mut self) -> Option<T> {
|
||||
mem::take(self).into_inner()
|
||||
}
|
||||
}
|
||||
|
||||
/// A value which is initialized on the first access.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// use std::lazy::Lazy;
|
||||
///
|
||||
/// let lazy: Lazy<i32> = Lazy::new(|| {
|
||||
/// println!("initializing");
|
||||
/// 92
|
||||
/// });
|
||||
/// println!("ready");
|
||||
/// println!("{}", *lazy);
|
||||
/// println!("{}", *lazy);
|
||||
///
|
||||
/// // Prints:
|
||||
/// // ready
|
||||
/// // initializing
|
||||
/// // 92
|
||||
/// // 92
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub struct Lazy<T, F = fn() -> T> {
|
||||
cell: OnceCell<T>,
|
||||
init: Cell<Option<F>>,
|
||||
}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T: fmt::Debug, F> fmt::Debug for Lazy<T, F> {
|
||||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||||
f.debug_struct("Lazy").field("cell", &self.cell).field("init", &"..").finish()
|
||||
}
|
||||
}
|
||||
|
||||
impl<T, F> Lazy<T, F> {
|
||||
/// Creates a new lazy value with the given initializing function.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// # fn main() {
|
||||
/// use std::lazy::Lazy;
|
||||
///
|
||||
/// let hello = "Hello, World!".to_string();
|
||||
///
|
||||
/// let lazy = Lazy::new(|| hello.to_uppercase());
|
||||
///
|
||||
/// assert_eq!(&*lazy, "HELLO, WORLD!");
|
||||
/// # }
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub const fn new(init: F) -> Lazy<T, F> {
|
||||
Lazy { cell: OnceCell::new(), init: Cell::new(Some(init)) }
|
||||
}
|
||||
}
|
||||
|
||||
impl<T, F: FnOnce() -> T> Lazy<T, F> {
|
||||
/// Forces the evaluation of this lazy value and returns a reference to
|
||||
/// the result.
|
||||
///
|
||||
/// This is equivalent to the `Deref` impl, but is explicit.
|
||||
///
|
||||
/// # Examples
|
||||
///
|
||||
/// ```
|
||||
/// #![feature(once_cell)]
|
||||
///
|
||||
/// use std::lazy::Lazy;
|
||||
///
|
||||
/// let lazy = Lazy::new(|| 92);
|
||||
///
|
||||
/// assert_eq!(Lazy::force(&lazy), &92);
|
||||
/// assert_eq!(&*lazy, &92);
|
||||
/// ```
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
pub fn force(this: &Lazy<T, F>) -> &T {
|
||||
this.cell.get_or_init(|| match this.init.take() {
|
||||
Some(f) => f(),
|
||||
None => panic!("`Lazy` instance has previously been poisoned"),
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
|
||||
type Target = T;
|
||||
fn deref(&self) -> &T {
|
||||
Lazy::force(self)
|
||||
}
|
||||
}
|
||||
|
||||
#[unstable(feature = "once_cell", issue = "74465")]
|
||||
impl<T: Default> Default for Lazy<T> {
|
||||
/// Creates a new lazy value using `Default` as the initializing function.
|
||||
fn default() -> Lazy<T> {
|
||||
Lazy::new(T::default)
|
||||
}
|
||||
}
|
||||
|
|
|
@ -1,6 +1,5 @@
|
|||
use core::{
|
||||
cell::Cell,
|
||||
lazy::{Lazy, OnceCell},
|
||||
cell::{Cell, LazyCell, OnceCell},
|
||||
sync::atomic::{AtomicUsize, Ordering::SeqCst},
|
||||
};
|
||||
|
||||
|
@ -91,7 +90,7 @@ fn into_inner() {
|
|||
#[test]
|
||||
fn lazy_new() {
|
||||
let called = Cell::new(0);
|
||||
let x = Lazy::new(|| {
|
||||
let x = LazyCell::new(|| {
|
||||
called.set(called.get() + 1);
|
||||
92
|
||||
});
|
||||
|
|
|
@ -1,5 +1,6 @@
|
|||
use crate::{
|
||||
lazy::{Lazy, SyncLazy, SyncOnceCell},
|
||||
cell::LazyCell,
|
||||
lazy::{SyncLazy, SyncOnceCell},
|
||||
panic,
|
||||
sync::{
|
||||
atomic::{AtomicUsize, Ordering::SeqCst},
|
||||
|
@ -21,7 +22,7 @@ fn default() -> Self {
|
|||
}
|
||||
}
|
||||
|
||||
let lazy: Lazy<Mutex<Foo>> = <_>::default();
|
||||
let lazy: LazyCell<Mutex<Foo>> = <_>::default();
|
||||
|
||||
assert_eq!(CALLED.load(SeqCst), 0);
|
||||
|
||||
|
@ -36,7 +37,7 @@ fn default() -> Self {
|
|||
|
||||
#[test]
|
||||
fn lazy_poisoning() {
|
||||
let x: Lazy<String> = Lazy::new(|| panic!("kaboom"));
|
||||
let x: LazyCell<String> = LazyCell::new(|| panic!("kaboom"));
|
||||
for _ in 0..2 {
|
||||
let res = panic::catch_unwind(panic::AssertUnwindSafe(|| x.len()));
|
||||
assert!(res.is_err());
|
||||
|
|
Loading…
Reference in a new issue