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Rollup merge of #98165 - WaffleLapkin:once_things_renamings, r=m-ou-se

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once cell renamings

This PR does the renamings proposed in https://github.com/rust-lang/rust/issues/74465#issuecomment-1153703128

- Move/rename `lazy::{OnceCell, Lazy}` to `cell::{OnceCell, LazyCell}`
- Move/rename `lazy::{SyncOnceCell, SyncLazy}` to `sync::{OnceLock, LazyLock}`

(I used `Lazy...` instead of `...Lazy` as it seems to be more consistent, easier to pronounce, etc)

```@rustbot``` label +T-libs-api -T-libs
This commit is contained in:
Matthias Krüger 2022-06-19 00:17:13 +02:00 committed by GitHub
commit f351f347b8
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GPG Key ID: 4AEE18F83AFDEB23
40 changed files with 1250 additions and 1215 deletions
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2
compiler/rustc_codegen_cranelift/src/driver/jit.rs
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@ -13,7 +13,7 @@ use rustc_span::Symbol;
use cranelift_jit::{JITBuilder, JITModule};
// FIXME use std::lazy::SyncOnceCell once it stabilizes
// FIXME use std::sync::OnceLock once it stabilizes
use once_cell::sync::OnceCell;
use crate::{prelude::*, BackendConfig};

2
compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
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@ -36,9 +36,9 @@ use rustc_target::abi::Size;
use libc::c_uint;
use smallvec::SmallVec;
use std::cell::OnceCell;
use std::cell::RefCell;
use std::iter;
use std::lazy::OnceCell;
use tracing::debug;
mod create_scope_map;

2
compiler/rustc_codegen_ssa/src/back/link.rs
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@ -38,11 +38,11 @@ use regex::Regex;
use tempfile::Builder as TempFileBuilder;
use std::borrow::Borrow;
use std::cell::OnceCell;
use std::collections::BTreeSet;
use std::ffi::OsString;
use std::fs::{File, OpenOptions};
use std::io::{BufWriter, Write};
use std::lazy::OnceCell;
use std::ops::Deref;
use std::path::{Path, PathBuf};
use std::process::{ExitStatus, Output, Stdio};

4
compiler/rustc_data_structures/src/jobserver.rs
View File

@ -1,5 +1,5 @@
pub use jobserver_crate::Client;
use std::lazy::SyncLazy;
use std::sync::LazyLock;
// We can only call `from_env` once per process
@ -18,7 +18,7 @@ use std::lazy::SyncLazy;
// Also note that we stick this in a global because there could be
// multiple rustc instances in this process, and the jobserver is
// per-process.
static GLOBAL_CLIENT: SyncLazy<Client> = SyncLazy::new(|| unsafe {
static GLOBAL_CLIENT: LazyLock<Client> = LazyLock::new(|| unsafe {
Client::from_env().unwrap_or_else(|| {
let client = Client::new(32).expect("failed to create jobserver");
// Acquire a token for the main thread which we can release later

4
compiler/rustc_data_structures/src/sync.rs
View File

@ -173,7 +173,7 @@ cfg_if! {
pub use std::cell::RefMut as LockGuard;
pub use std::cell::RefMut as MappedLockGuard;
pub use std::lazy::OnceCell;
pub use std::cell::OnceCell;
use std::cell::RefCell as InnerRwLock;
use std::cell::RefCell as InnerLock;
@ -258,7 +258,7 @@ cfg_if! {
pub use parking_lot::MutexGuard as LockGuard;
pub use parking_lot::MappedMutexGuard as MappedLockGuard;
pub use std::lazy::SyncOnceCell as OnceCell;
pub use std::sync::OnceLock as OnceCell;
pub use std::sync::atomic::{AtomicBool, AtomicUsize, AtomicU32, AtomicU64};

8
compiler/rustc_driver/src/lib.rs
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@ -47,11 +47,11 @@ use std::env;
use std::ffi::OsString;
use std::fs;
use std::io::{self, Read, Write};
use std::lazy::SyncLazy;
use std::panic::{self, catch_unwind};
use std::path::PathBuf;
use std::process::{self, Command, Stdio};
use std::str;
use std::sync::LazyLock;
use std::time::Instant;
pub mod args;
@ -1141,8 +1141,8 @@ pub fn catch_with_exit_code(f: impl FnOnce() -> interface::Result<()>) -> i32 {
}
}
static DEFAULT_HOOK: SyncLazy<Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send + 'static>> =
SyncLazy::new(|| {
static DEFAULT_HOOK: LazyLock<Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send + 'static>> =
LazyLock::new(|| {
let hook = panic::take_hook();
panic::set_hook(Box::new(|info| {
// Invoke the default handler, which prints the actual panic message and optionally a backtrace
@ -1237,7 +1237,7 @@ pub fn install_ice_hook() {
if std::env::var("RUST_BACKTRACE").is_err() {
std::env::set_var("RUST_BACKTRACE", "full");
}
SyncLazy::force(&DEFAULT_HOOK);
LazyLock::force(&DEFAULT_HOOK);
}
/// This allows tools to enable rust logging without having to magically match rustc's

4
compiler/rustc_error_messages/src/lib.rs
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@ -18,9 +18,9 @@ use std::path::{Path, PathBuf};
use tracing::{instrument, trace};
#[cfg(not(parallel_compiler))]
use std::lazy::Lazy;
use std::cell::LazyCell as Lazy;
#[cfg(parallel_compiler)]
use std::lazy::SyncLazy as Lazy;
use std::sync::LazyLock as Lazy;
#[cfg(parallel_compiler)]
use intl_memoizer::concurrent::IntlLangMemoizer;

6
compiler/rustc_feature/src/builtin_attrs.rs
View File

@ -9,7 +9,7 @@ use crate::{Features, Stability};
use rustc_data_structures::fx::FxHashMap;
use rustc_span::symbol::{sym, Symbol};
use std::lazy::SyncLazy;
use std::sync::LazyLock;
type GateFn = fn(&Features) -> bool;
@ -809,8 +809,8 @@ pub fn is_builtin_only_local(name: Symbol) -> bool {
BUILTIN_ATTRIBUTE_MAP.get(&name).map_or(false, |attr| attr.only_local)
}
pub static BUILTIN_ATTRIBUTE_MAP: SyncLazy<FxHashMap<Symbol, &BuiltinAttribute>> =
SyncLazy::new(|| {
pub static BUILTIN_ATTRIBUTE_MAP: LazyLock<FxHashMap<Symbol, &BuiltinAttribute>> =
LazyLock::new(|| {
let mut map = FxHashMap::default();
for attr in BUILTIN_ATTRIBUTES.iter() {
if map.insert(attr.name, attr).is_some() {

4
compiler/rustc_hir/src/lang_items.rs
View File

@ -17,7 +17,7 @@ use rustc_macros::HashStable_Generic;
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_span::Span;
use std::lazy::SyncLazy;
use std::sync::LazyLock;
pub enum LangItemGroup {
Op,
@ -134,7 +134,7 @@ macro_rules! language_item_table {
}
/// A mapping from the name of the lang item to its order and the form it must be of.
pub static ITEM_REFS: SyncLazy<FxHashMap<Symbol, (usize, Target)>> = SyncLazy::new(|| {
pub static ITEM_REFS: LazyLock<FxHashMap<Symbol, (usize, Target)>> = LazyLock::new(|| {
let mut item_refs = FxHashMap::default();
$( item_refs.insert($module::$name, (LangItem::$variant as usize, $target)); )*
item_refs

4
compiler/rustc_hir/src/weak_lang_items.rs
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@ -7,12 +7,12 @@ use rustc_ast as ast;
use rustc_data_structures::stable_map::StableMap;
use rustc_span::symbol::{sym, Symbol};
use std::lazy::SyncLazy;
use std::sync::LazyLock;
macro_rules! weak_lang_items {
($($name:ident, $item:ident, $sym:ident;)*) => (
pub static WEAK_ITEMS_REFS: SyncLazy<StableMap<Symbol, LangItem>> = SyncLazy::new(|| {
pub static WEAK_ITEMS_REFS: LazyLock<StableMap<Symbol, LangItem>> = LazyLock::new(|| {
let mut map = StableMap::default();
$(map.insert(sym::$name, LangItem::$item);)*
map

6
compiler/rustc_interface/src/passes.rs
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@ -44,11 +44,11 @@ use std::any::Any;
use std::cell::RefCell;
use std::ffi::OsString;
use std::io::{self, BufWriter, Write};
use std::lazy::SyncLazy;
use std::marker::PhantomPinned;
use std::path::{Path, PathBuf};
use std::pin::Pin;
use std::rc::Rc;
use std::sync::LazyLock;
use std::{env, fs, iter};
pub fn parse<'a>(sess: &'a Session, input: &Input) -> PResult<'a, ast::Crate> {
@ -774,7 +774,7 @@ pub fn prepare_outputs(
Ok(outputs)
}
pub static DEFAULT_QUERY_PROVIDERS: SyncLazy<Providers> = SyncLazy::new(|| {
pub static DEFAULT_QUERY_PROVIDERS: LazyLock<Providers> = LazyLock::new(|| {
let providers = &mut Providers::default();
providers.analysis = analysis;
proc_macro_decls::provide(providers);
@ -799,7 +799,7 @@ pub static DEFAULT_QUERY_PROVIDERS: SyncLazy<Providers> = SyncLazy::new(|| {
*providers
});
pub static DEFAULT_EXTERN_QUERY_PROVIDERS: SyncLazy<ExternProviders> = SyncLazy::new(|| {
pub static DEFAULT_EXTERN_QUERY_PROVIDERS: LazyLock<ExternProviders> = LazyLock::new(|| {
let mut extern_providers = ExternProviders::default();
rustc_metadata::provide_extern(&mut extern_providers);
rustc_codegen_ssa::provide_extern(&mut extern_providers);

6
compiler/rustc_interface/src/util.rs
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@ -24,12 +24,12 @@ use rustc_span::source_map::FileLoader;
use rustc_span::symbol::{sym, Symbol};
use std::env;
use std::env::consts::{DLL_PREFIX, DLL_SUFFIX};
use std::lazy::SyncOnceCell;
use std::mem;
#[cfg(not(parallel_compiler))]
use std::panic;
use std::path::{Path, PathBuf};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::OnceLock;
use std::thread;
use tracing::info;
@ -242,7 +242,7 @@ pub fn get_codegen_backend(
maybe_sysroot: &Option<PathBuf>,
backend_name: Option<&str>,
) -> Box<dyn CodegenBackend> {
static LOAD: SyncOnceCell<unsafe fn() -> Box<dyn CodegenBackend>> = SyncOnceCell::new();
static LOAD: OnceLock<unsafe fn() -> Box<dyn CodegenBackend>> = OnceLock::new();
let load = LOAD.get_or_init(|| {
let default_codegen_backend = option_env!("CFG_DEFAULT_CODEGEN_BACKEND").unwrap_or("llvm");
@ -265,7 +265,7 @@ pub fn get_codegen_backend(
// loading, so we leave the code here. It is potentially useful for other tools
// that want to invoke the rustc binary while linking to rustc as well.
pub fn rustc_path<'a>() -> Option<&'a Path> {
static RUSTC_PATH: SyncOnceCell<Option<PathBuf>> = SyncOnceCell::new();
static RUSTC_PATH: OnceLock<Option<PathBuf>> = OnceLock::new();
const BIN_PATH: &str = env!("RUSTC_INSTALL_BINDIR");

4
compiler/rustc_mir_dataflow/src/framework/graphviz.rs
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@ -1,7 +1,7 @@
//! A helpful diagram for debugging dataflow problems.
use std::borrow::Cow;
use std::lazy::SyncOnceCell;
use std::sync::OnceLock;
use std::{io, ops, str};
use regex::Regex;
@ -590,7 +590,7 @@ where
macro_rules! regex {
($re:literal $(,)?) => {{
static RE: SyncOnceCell<regex::Regex> = SyncOnceCell::new();
static RE: OnceLock<regex::Regex> = OnceLock::new();
RE.get_or_init(|| Regex::new($re).unwrap())
}};
}

4
compiler/rustc_mir_transform/src/coverage/debug.rs
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@ -123,15 +123,15 @@ use rustc_middle::ty::TyCtxt;
use rustc_span::Span;
use std::iter;
use std::lazy::SyncOnceCell;
use std::ops::Deref;
use std::sync::OnceLock;
pub const NESTED_INDENT: &str = " ";
const RUSTC_COVERAGE_DEBUG_OPTIONS: &str = "RUSTC_COVERAGE_DEBUG_OPTIONS";
pub(super) fn debug_options<'a>() -> &'a DebugOptions {
static DEBUG_OPTIONS: SyncOnceCell<DebugOptions> = SyncOnceCell::new();
static DEBUG_OPTIONS: OnceLock<DebugOptions> = OnceLock::new();
&DEBUG_OPTIONS.get_or_init(DebugOptions::from_env)
}

4
compiler/rustc_typeck/src/check/wfcheck.rs
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@ -29,9 +29,9 @@ use rustc_span::{Span, DUMMY_SP};
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
use rustc_trait_selection::traits::{self, ObligationCause, ObligationCauseCode, WellFormedLoc};
use std::cell::LazyCell;
use std::convert::TryInto;
use std::iter;
use std::lazy::Lazy;
use std::ops::ControlFlow;
/// Helper type of a temporary returned by `.for_item(...)`.
@ -1728,7 +1728,7 @@ fn check_variances_for_type_defn<'tcx>(
identify_constrained_generic_params(tcx, ty_predicates, None, &mut constrained_parameters);
// Lazily calculated because it is only needed in case of an error.
let explicitly_bounded_params = Lazy::new(|| {
let explicitly_bounded_params = LazyCell::new(|| {
let icx = crate::collect::ItemCtxt::new(tcx, item.def_id.to_def_id());
hir_generics
.predicates

8
library/core/src/cell.rs
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@ -199,6 +199,14 @@ use crate::mem;
use crate::ops::{CoerceUnsized, Deref, DerefMut};
use crate::ptr::{self, NonNull};
mod lazy;
mod once;
#[unstable(feature = "once_cell", issue = "74465")]
pub use lazy::LazyCell;
#[unstable(feature = "once_cell", issue = "74465")]
pub use once::OnceCell;
/// A mutable memory location.
///
/// # Examples

104
library/core/src/cell/lazy.rs Normal file
View File

@ -0,0 +1,104 @@
use crate::cell::{Cell, OnceCell};
use crate::fmt;
use crate::ops::Deref;
/// A value which is initialized on the first access.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::cell::LazyCell;
///
/// let lazy: LazyCell<i32> = LazyCell::new(|| {
/// println!("initializing");
/// 92
/// });
/// println!("ready");
/// println!("{}", *lazy);
/// println!("{}", *lazy);
///
/// // Prints:
/// // ready
/// // initializing
/// // 92
/// // 92
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub struct LazyCell<T, F = fn() -> T> {
cell: OnceCell<T>,
init: Cell<Option<F>>,
}
impl<T, F> LazyCell<T, F> {
/// Creates a new lazy value with the given initializing function.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::cell::LazyCell;
///
/// let hello = "Hello, World!".to_string();
///
/// let lazy = LazyCell::new(|| hello.to_uppercase());
///
/// assert_eq!(&*lazy, "HELLO, WORLD!");
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub const fn new(init: F) -> LazyCell<T, F> {
LazyCell { cell: OnceCell::new(), init: Cell::new(Some(init)) }
}
}
impl<T, F: FnOnce() -> T> LazyCell<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::cell::LazyCell;
///
/// let lazy = LazyCell::new(|| 92);
///
/// assert_eq!(LazyCell::force(&lazy), &92);
/// assert_eq!(&*lazy, &92);
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub fn force(this: &LazyCell<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 LazyCell<T, F> {
type Target = T;
fn deref(&self) -> &T {
LazyCell::force(self)
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: Default> Default for LazyCell<T> {
/// Creates a new lazy value using `Default` as the initializing function.
fn default() -> LazyCell<T> {
LazyCell::new(T::default)
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: fmt::Debug, F> fmt::Debug for LazyCell<T, F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Lazy").field("cell", &self.cell).field("init", &"..").finish()
}
}

283
library/core/src/cell/once.rs Normal file
View File

@ -0,0 +1,283 @@
use crate::cell::UnsafeCell;
use crate::fmt;
use crate::mem;
/// 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::cell::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>>,
}
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::cell::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::cell::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::cell::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::cell::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::cell::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()
}
}
#[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)) }
}
}

388
library/core/src/lazy.rs
View File

@ -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)
}
}

5
library/core/tests/lazy.rs
View File

@ -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
});

9
library/std/src/io/stdio.rs
View File

@ -8,10 +8,9 @@ use crate::io::prelude::*;
use crate::cell::{Cell, RefCell};
use crate::fmt;
use crate::io::{self, BufReader, IoSlice, IoSliceMut, LineWriter, Lines};
use crate::lazy::SyncOnceCell;
use crate::pin::Pin;
use crate::sync::atomic::{AtomicBool, Ordering};
use crate::sync::{Arc, Mutex, MutexGuard};
use crate::sync::{Arc, Mutex, MutexGuard, OnceLock};
use crate::sys::stdio;
use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
@ -318,7 +317,7 @@ pub struct StdinLock<'a> {
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn stdin() -> Stdin {
static INSTANCE: SyncOnceCell<Mutex<BufReader<StdinRaw>>> = SyncOnceCell::new();
static INSTANCE: OnceLock<Mutex<BufReader<StdinRaw>>> = OnceLock::new();
Stdin {
inner: INSTANCE.get_or_init(|| {
Mutex::new(BufReader::with_capacity(stdio::STDIN_BUF_SIZE, stdin_raw()))
@ -552,7 +551,7 @@ pub struct StdoutLock<'a> {
inner: ReentrantMutexGuard<'a, RefCell<LineWriter<StdoutRaw>>>,
}
static STDOUT: SyncOnceCell<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> = SyncOnceCell::new();
static STDOUT: OnceLock<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> = OnceLock::new();
/// Constructs a new handle to the standard output of the current process.
///
@ -837,7 +836,7 @@ pub fn stderr() -> Stderr {
// Note that unlike `stdout()` we don't use `at_exit` here to register a
// destructor. Stderr is not buffered , so there's no need to run a
// destructor for flushing the buffer
static INSTANCE: SyncOnceCell<ReentrantMutex<RefCell<StderrRaw>>> = SyncOnceCell::new();
static INSTANCE: OnceLock<ReentrantMutex<RefCell<StderrRaw>>> = OnceLock::new();
Stderr {
inner: Pin::static_ref(&INSTANCE).get_or_init_pin(

616
library/std/src/lazy.rs
View File

@ -1,617 +1 @@
//! Lazy values and one-time initialization of static data.
#[cfg(test)]
mod tests;
use crate::{
cell::{Cell, UnsafeCell},
fmt,
marker::PhantomData,
mem::MaybeUninit,
ops::{Deref, Drop},
panic::{RefUnwindSafe, UnwindSafe},
pin::Pin,
sync::Once,
};
#[doc(inline)]
#[unstable(feature = "once_cell", issue = "74465")]
pub use core::lazy::*;
/// A synchronization primitive which can be written to only once.
///
/// This type is a thread-safe `OnceCell`.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// static CELL: SyncOnceCell<String> = SyncOnceCell::new();
/// assert!(CELL.get().is_none());
///
/// std::thread::spawn(|| {
/// let value: &String = CELL.get_or_init(|| {
/// "Hello, World!".to_string()
/// });
/// assert_eq!(value, "Hello, World!");
/// }).join().unwrap();
///
/// let value: Option<&String> = CELL.get();
/// assert!(value.is_some());
/// assert_eq!(value.unwrap().as_str(), "Hello, World!");
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub struct SyncOnceCell<T> {
once: Once,
// Whether or not the value is initialized is tracked by `state_and_queue`.
value: UnsafeCell<MaybeUninit<T>>,
/// `PhantomData` to make sure dropck understands we're dropping T in our Drop impl.
///
/// ```compile_fail,E0597
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// struct A<'a>(&'a str);
///
/// impl<'a> Drop for A<'a> {
/// fn drop(&mut self) {}
/// }
///
/// let cell = SyncOnceCell::new();
/// {
/// let s = String::new();
/// let _ = cell.set(A(&s));
/// }
/// ```
_marker: PhantomData<T>,
}
// Why do we need `T: Send`?
// Thread A creates a `SyncOnceCell` and shares it with
// scoped thread B, which fills the cell, which is
// then destroyed by A. That is, destructor observes
// a sent value.
#[unstable(feature = "once_cell", issue = "74465")]
unsafe impl<T: Sync + Send> Sync for SyncOnceCell<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
unsafe impl<T: Send> Send for SyncOnceCell<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: RefUnwindSafe + UnwindSafe> RefUnwindSafe for SyncOnceCell<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: UnwindSafe> UnwindSafe for SyncOnceCell<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
impl<T> const Default for SyncOnceCell<T> {
/// Creates a new empty cell.
///
/// # Example
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// fn main() {
/// assert_eq!(SyncOnceCell::<()>::new(), SyncOnceCell::default());
/// }
/// ```
fn default() -> SyncOnceCell<T> {
SyncOnceCell::new()
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: fmt::Debug> fmt::Debug for SyncOnceCell<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self.get() {
Some(v) => f.debug_tuple("Once").field(v).finish(),
None => f.write_str("Once(Uninit)"),
}
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: Clone> Clone for SyncOnceCell<T> {
fn clone(&self) -> SyncOnceCell<T> {
let cell = Self::new();
if let Some(value) = self.get() {
match cell.set(value.clone()) {
Ok(()) => (),
Err(_) => unreachable!(),
}
}
cell
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T> From<T> for SyncOnceCell<T> {
/// Create a new cell with its contents set to `value`.
///
/// # Example
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// # fn main() -> Result<(), i32> {
/// let a = SyncOnceCell::from(3);
/// let b = SyncOnceCell::new();
/// b.set(3)?;
/// assert_eq!(a, b);
/// Ok(())
/// # }
/// ```
fn from(value: T) -> Self {
let cell = Self::new();
match cell.set(value) {
Ok(()) => cell,
Err(_) => unreachable!(),
}
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: PartialEq> PartialEq for SyncOnceCell<T> {
fn eq(&self, other: &SyncOnceCell<T>) -> bool {
self.get() == other.get()
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: Eq> Eq for SyncOnceCell<T> {}
impl<T> SyncOnceCell<T> {
/// Creates a new empty cell.
#[unstable(feature = "once_cell", issue = "74465")]
#[must_use]
pub const fn new() -> SyncOnceCell<T> {
SyncOnceCell {
once: Once::new(),
value: UnsafeCell::new(MaybeUninit::uninit()),
_marker: PhantomData,
}
}
/// Gets the reference to the underlying value.
///
/// Returns `None` if the cell is empty, or being initialized. This
/// method never blocks.
#[unstable(feature = "once_cell", issue = "74465")]
pub fn get(&self) -> Option<&T> {
if self.is_initialized() {
// Safe b/c checked is_initialized
Some(unsafe { self.get_unchecked() })
} else {
None
}
}
/// Gets the mutable reference to the underlying value.
///
/// Returns `None` if the cell is empty. This method never blocks.
#[unstable(feature = "once_cell", issue = "74465")]
pub fn get_mut(&mut self) -> Option<&mut T> {
if self.is_initialized() {
// Safe b/c checked is_initialized and we have a unique access
Some(unsafe { self.get_unchecked_mut() })
} else {
None
}
}
/// Sets the contents of this cell to `value`.
///
/// May block if another thread is currently attempting to initialize the cell. The cell is
/// guaranteed to contain a value when set returns, though not necessarily the one provided.
///
/// Returns `Ok(())` if the cell's value was set by this call.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// static CELL: SyncOnceCell<i32> = SyncOnceCell::new();
///
/// fn main() {
/// assert!(CELL.get().is_none());
///
/// std::thread::spawn(|| {
/// assert_eq!(CELL.set(92), Ok(()));
/// }).join().unwrap();
///
/// assert_eq!(CELL.set(62), Err(62));
/// assert_eq!(CELL.get(), Some(&92));
/// }
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub fn set(&self, value: T) -> Result<(), T> {
let mut value = Some(value);
self.get_or_init(|| value.take().unwrap());
match value {
None => Ok(()),
Some(value) => Err(value),
}
}
/// Gets the contents of the cell, initializing it with `f` if the cell
/// was empty.
///
/// Many threads may call `get_or_init` concurrently with different
/// initializing functions, but it is guaranteed that only one function
/// will be executed.
///
/// # 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`. The
/// exact outcome is unspecified. Current implementation deadlocks, but
/// this may be changed to a panic in the future.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// let cell = SyncOnceCell::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`.
/// The exact outcome is unspecified. Current implementation
/// deadlocks, but this may be changed to a panic in the future.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// let cell = SyncOnceCell::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>,
{
// Fast path check
// NOTE: We need to perform an acquire on the state in this method
// in order to correctly synchronize `SyncLazy::force`. This is
// currently done by calling `self.get()`, which in turn calls
// `self.is_initialized()`, which in turn performs the acquire.
if let Some(value) = self.get() {
return Ok(value);
}
self.initialize(f)?;
debug_assert!(self.is_initialized());
// SAFETY: The inner value has been initialized
Ok(unsafe { self.get_unchecked() })
}
/// Internal-only API that gets the contents of the cell, initializing it
/// in two steps with `f` and `g` if the cell was empty.
///
/// `f` is called to construct the value, which is then moved into the cell
/// and given as a (pinned) mutable reference to `g` to finish
/// initialization.
///
/// This allows `g` to inspect an manipulate the value after it has been
/// moved into its final place in the cell, but before the cell is
/// considered initialized.
///
/// # Panics
///
/// If `f` or `g` panics, the panic is propagated to the caller, and the
/// cell remains uninitialized.
///
/// With the current implementation, if `g` panics, the value from `f` will
/// not be dropped. This should probably be fixed if this is ever used for
/// a type where this matters.
///
/// It is an error to reentrantly initialize the cell from `f`. The exact
/// outcome is unspecified. Current implementation deadlocks, but this may
/// be changed to a panic in the future.
pub(crate) fn get_or_init_pin<F, G>(self: Pin<&Self>, f: F, g: G) -> Pin<&T>
where
F: FnOnce() -> T,
G: FnOnce(Pin<&mut T>),
{
if let Some(value) = self.get_ref().get() {
// SAFETY: The inner value was already initialized, and will not be
// moved anymore.
return unsafe { Pin::new_unchecked(value) };
}
let slot = &self.value;
// Ignore poisoning from other threads
// If another thread panics, then we'll be able to run our closure
self.once.call_once_force(|_| {
let value = f();
// SAFETY: We use the Once (self.once) to guarantee unique access
// to the UnsafeCell (slot).
let value: &mut T = unsafe { (&mut *slot.get()).write(value) };
// SAFETY: The value has been written to its final place in
// self.value. We do not to move it anymore, which we promise here
// with a Pin<&mut T>.
g(unsafe { Pin::new_unchecked(value) });
});
// SAFETY: The inner value has been initialized, and will not be moved
// anymore.
unsafe { Pin::new_unchecked(self.get_ref().get_unchecked()) }
}
/// Consumes the `SyncOnceCell`, returning the wrapped value. Returns
/// `None` if the cell was empty.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// let cell: SyncOnceCell<String> = SyncOnceCell::new();
/// assert_eq!(cell.into_inner(), None);
///
/// let cell = SyncOnceCell::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(mut self) -> Option<T> {
self.take()
}
/// Takes the value out of this `SyncOnceCell`, moving it back to an uninitialized state.
///
/// Has no effect and returns `None` if the `SyncOnceCell` hasn't been initialized.
///
/// Safety is guaranteed by requiring a mutable reference.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncOnceCell;
///
/// let mut cell: SyncOnceCell<String> = SyncOnceCell::new();
/// assert_eq!(cell.take(), None);
///
/// let mut cell = SyncOnceCell::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> {
if self.is_initialized() {
self.once = Once::new();
// SAFETY: `self.value` is initialized and contains a valid `T`.
// `self.once` is reset, so `is_initialized()` will be false again
// which prevents the value from being read twice.
unsafe { Some((&mut *self.value.get()).assume_init_read()) }
} else {
None
}
}
#[inline]
fn is_initialized(&self) -> bool {
self.once.is_completed()
}
#[cold]
fn initialize<F, E>(&self, f: F) -> Result<(), E>
where
F: FnOnce() -> Result<T, E>,
{
let mut res: Result<(), E> = Ok(());
let slot = &self.value;
// Ignore poisoning from other threads
// If another thread panics, then we'll be able to run our closure
self.once.call_once_force(|p| {
match f() {
Ok(value) => {
unsafe { (&mut *slot.get()).write(value) };
}
Err(e) => {
res = Err(e);
// Treat the underlying `Once` as poisoned since we
// failed to initialize our value. Calls
p.poison();
}
}
});
res
}
/// # Safety
///
/// The value must be initialized
unsafe fn get_unchecked(&self) -> &T {
debug_assert!(self.is_initialized());
(&*self.value.get()).assume_init_ref()
}
/// # Safety
///
/// The value must be initialized
unsafe fn get_unchecked_mut(&mut self) -> &mut T {
debug_assert!(self.is_initialized());
(&mut *self.value.get()).assume_init_mut()
}
}
unsafe impl<#[may_dangle] T> Drop for SyncOnceCell<T> {
fn drop(&mut self) {
if self.is_initialized() {
// SAFETY: The cell is initialized and being dropped, so it can't
// be accessed again. We also don't touch the `T` other than
// dropping it, which validates our usage of #[may_dangle].
unsafe { (&mut *self.value.get()).assume_init_drop() };
}
}
}
/// A value which is initialized on the first access.
///
/// This type is a thread-safe `Lazy`, and can be used in statics.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::collections::HashMap;
///
/// use std::lazy::SyncLazy;
///
/// static HASHMAP: SyncLazy<HashMap<i32, String>> = SyncLazy::new(|| {
/// println!("initializing");
/// let mut m = HashMap::new();
/// m.insert(13, "Spica".to_string());
/// m.insert(74, "Hoyten".to_string());
/// m
/// });
///
/// fn main() {
/// println!("ready");
/// std::thread::spawn(|| {
/// println!("{:?}", HASHMAP.get(&13));
/// }).join().unwrap();
/// println!("{:?}", HASHMAP.get(&74));
///
/// // Prints:
/// // ready
/// // initializing
/// // Some("Spica")
/// // Some("Hoyten")
/// }
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub struct SyncLazy<T, F = fn() -> T> {
cell: SyncOnceCell<T>,
init: Cell<Option<F>>,
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: fmt::Debug, F> fmt::Debug for SyncLazy<T, F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Lazy").field("cell", &self.cell).finish_non_exhaustive()
}
}
// We never create a `&F` from a `&SyncLazy<T, F>` so it is fine
// to not impl `Sync` for `F`
// we do create a `&mut Option<F>` in `force`, but this is
// properly synchronized, so it only happens once
// so it also does not contribute to this impl.
#[unstable(feature = "once_cell", issue = "74465")]
unsafe impl<T, F: Send> Sync for SyncLazy<T, F> where SyncOnceCell<T>: Sync {}
// auto-derived `Send` impl is OK.
#[unstable(feature = "once_cell", issue = "74465")]
impl<T, F: UnwindSafe> RefUnwindSafe for SyncLazy<T, F> where SyncOnceCell<T>: RefUnwindSafe {}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T, F: UnwindSafe> UnwindSafe for SyncLazy<T, F> where SyncOnceCell<T>: UnwindSafe {}
impl<T, F> SyncLazy<T, F> {
/// Creates a new lazy value with the given initializing
/// function.
#[unstable(feature = "once_cell", issue = "74465")]
pub const fn new(f: F) -> SyncLazy<T, F> {
SyncLazy { cell: SyncOnceCell::new(), init: Cell::new(Some(f)) }
}
}
impl<T, F: FnOnce() -> T> SyncLazy<T, F> {
/// Forces the evaluation of this lazy value and
/// returns a reference to result. This is equivalent
/// to the `Deref` impl, but is explicit.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::lazy::SyncLazy;
///
/// let lazy = SyncLazy::new(|| 92);
///
/// assert_eq!(SyncLazy::force(&lazy), &92);
/// assert_eq!(&*lazy, &92);
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub fn force(this: &SyncLazy<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 SyncLazy<T, F> {
type Target = T;
fn deref(&self) -> &T {
SyncLazy::force(self)
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: Default> Default for SyncLazy<T> {
/// Creates a new lazy value using `Default` as the initializing function.
fn default() -> SyncLazy<T> {
SyncLazy::new(T::default)
}
}

121
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@ -0,0 +1,121 @@
use crate::cell::Cell;
use crate::fmt;
use crate::ops::Deref;
use crate::panic::{RefUnwindSafe, UnwindSafe};
use crate::sync::OnceLock;
/// A value which is initialized on the first access.
///
/// This type is a thread-safe `Lazy`, and can be used in statics.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::collections::HashMap;
///
/// use std::sync::LazyLock;
///
/// static HASHMAP: LazyLock<HashMap<i32, String>> = LazyLock::new(|| {
/// println!("initializing");
/// let mut m = HashMap::new();
/// m.insert(13, "Spica".to_string());
/// m.insert(74, "Hoyten".to_string());
/// m
/// });
///
/// fn main() {
/// println!("ready");
/// std::thread::spawn(|| {
/// println!("{:?}", HASHMAP.get(&13));
/// }).join().unwrap();
/// println!("{:?}", HASHMAP.get(&74));
///
/// // Prints:
/// // ready
/// // initializing
/// // Some("Spica")
/// // Some("Hoyten")
/// }
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub struct LazyLock<T, F = fn() -> T> {
cell: OnceLock<T>,
init: Cell<Option<F>>,
}
impl<T, F> LazyLock<T, F> {
/// Creates a new lazy value with the given initializing
/// function.
#[unstable(feature = "once_cell", issue = "74465")]
pub const fn new(f: F) -> LazyLock<T, F> {
LazyLock { cell: OnceLock::new(), init: Cell::new(Some(f)) }
}
}
impl<T, F: FnOnce() -> T> LazyLock<T, F> {
/// Forces the evaluation of this lazy value and
/// returns a reference to result. This is equivalent
/// to the `Deref` impl, but is explicit.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::LazyLock;
///
/// let lazy = LazyLock::new(|| 92);
///
/// assert_eq!(LazyLock::force(&lazy), &92);
/// assert_eq!(&*lazy, &92);
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub fn force(this: &LazyLock<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 LazyLock<T, F> {
type Target = T;
fn deref(&self) -> &T {
LazyLock::force(self)
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: Default> Default for LazyLock<T> {
/// Creates a new lazy value using `Default` as the initializing function.
fn default() -> LazyLock<T> {
LazyLock::new(T::default)
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: fmt::Debug, F> fmt::Debug for LazyLock<T, F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Lazy").field("cell", &self.cell).finish_non_exhaustive()
}
}
// We never create a `&F` from a `&LazyLock<T, F>` so it is fine
// to not impl `Sync` for `F`
// we do create a `&mut Option<F>` in `force`, but this is
// properly synchronized, so it only happens once
// so it also does not contribute to this impl.
#[unstable(feature = "once_cell", issue = "74465")]
unsafe impl<T, F: Send> Sync for LazyLock<T, F> where OnceLock<T>: Sync {}
// auto-derived `Send` impl is OK.
#[unstable(feature = "once_cell", issue = "74465")]
impl<T, F: UnwindSafe> RefUnwindSafe for LazyLock<T, F> where OnceLock<T>: RefUnwindSafe {}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T, F: UnwindSafe> UnwindSafe for LazyLock<T, F> where OnceLock<T>: UnwindSafe {}
#[cfg(test)]
mod tests;

143
library/std/src/sync/lazy_lock/tests.rs Normal file
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@ -0,0 +1,143 @@
use crate::{
cell::LazyCell,
panic,
sync::{
atomic::{AtomicUsize, Ordering::SeqCst},
Mutex,
},
sync::{LazyLock, OnceLock},
thread,
};
fn spawn_and_wait<R: Send + 'static>(f: impl FnOnce() -> R + Send + 'static) -> R {
thread::spawn(f).join().unwrap()
}
#[test]
fn lazy_default() {
static CALLED: AtomicUsize = AtomicUsize::new(0);
struct Foo(u8);
impl Default for Foo {
fn default() -> Self {
CALLED.fetch_add(1, SeqCst);
Foo(42)
}
}
let lazy: LazyCell<Mutex<Foo>> = <_>::default();
assert_eq!(CALLED.load(SeqCst), 0);
assert_eq!(lazy.lock().unwrap().0, 42);
assert_eq!(CALLED.load(SeqCst), 1);
lazy.lock().unwrap().0 = 21;
assert_eq!(lazy.lock().unwrap().0, 21);
assert_eq!(CALLED.load(SeqCst), 1);
}
#[test]
fn lazy_poisoning() {
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());
}
}
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn sync_lazy_new() {
static CALLED: AtomicUsize = AtomicUsize::new(0);
static SYNC_LAZY: LazyLock<i32> = LazyLock::new(|| {
CALLED.fetch_add(1, SeqCst);
92
});
assert_eq!(CALLED.load(SeqCst), 0);
spawn_and_wait(|| {
let y = *SYNC_LAZY - 30;
assert_eq!(y, 62);
assert_eq!(CALLED.load(SeqCst), 1);
});
let y = *SYNC_LAZY - 30;
assert_eq!(y, 62);
assert_eq!(CALLED.load(SeqCst), 1);
}
#[test]
fn sync_lazy_default() {
static CALLED: AtomicUsize = AtomicUsize::new(0);
struct Foo(u8);
impl Default for Foo {
fn default() -> Self {
CALLED.fetch_add(1, SeqCst);
Foo(42)
}
}
let lazy: LazyLock<Mutex<Foo>> = <_>::default();
assert_eq!(CALLED.load(SeqCst), 0);
assert_eq!(lazy.lock().unwrap().0, 42);
assert_eq!(CALLED.load(SeqCst), 1);
lazy.lock().unwrap().0 = 21;
assert_eq!(lazy.lock().unwrap().0, 21);
assert_eq!(CALLED.load(SeqCst), 1);
}
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn static_sync_lazy() {
static XS: LazyLock<Vec<i32>> = LazyLock::new(|| {
let mut xs = Vec::new();
xs.push(1);
xs.push(2);
xs.push(3);
xs
});
spawn_and_wait(|| {
assert_eq!(&*XS, &vec![1, 2, 3]);
});
assert_eq!(&*XS, &vec![1, 2, 3]);
}
#[test]
fn static_sync_lazy_via_fn() {
fn xs() -> &'static Vec<i32> {
static XS: OnceLock<Vec<i32>> = OnceLock::new();
XS.get_or_init(|| {
let mut xs = Vec::new();
xs.push(1);
xs.push(2);
xs.push(3);
xs
})
}
assert_eq!(xs(), &vec![1, 2, 3]);
}
#[test]
fn sync_lazy_poisoning() {
let x: LazyLock<String> = LazyLock::new(|| panic!("kaboom"));
for _ in 0..2 {
let res = panic::catch_unwind(|| x.len());
assert!(res.is_err());
}
}
#[test]
fn is_sync_send() {
fn assert_traits<T: Send + Sync>() {}
assert_traits::<LazyLock<String>>();
}

7
library/std/src/sync/mod.rs
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@ -170,11 +170,18 @@ pub use self::poison::{LockResult, PoisonError, TryLockError, TryLockResult};
#[stable(feature = "rust1", since = "1.0.0")]
pub use self::rwlock::{RwLock, RwLockReadGuard, RwLockWriteGuard};
#[unstable(feature = "once_cell", issue = "74465")]
pub use self::lazy_lock::LazyLock;
#[unstable(feature = "once_cell", issue = "74465")]
pub use self::once_lock::OnceLock;
pub mod mpsc;
mod barrier;
mod condvar;
mod lazy_lock;
mod mutex;
mod once;
mod once_lock;
mod poison;
mod rwlock;

496
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@ -0,0 +1,496 @@
use crate::cell::UnsafeCell;
use crate::fmt;
use crate::marker::PhantomData;
use crate::mem::MaybeUninit;
use crate::panic::{RefUnwindSafe, UnwindSafe};
use crate::pin::Pin;
use crate::sync::Once;
/// A synchronization primitive which can be written to only once.
///
/// This type is a thread-safe `OnceCell`.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// static CELL: OnceLock<String> = OnceLock::new();
/// assert!(CELL.get().is_none());
///
/// std::thread::spawn(|| {
/// let value: &String = CELL.get_or_init(|| {
/// "Hello, World!".to_string()
/// });
/// assert_eq!(value, "Hello, World!");
/// }).join().unwrap();
///
/// let value: Option<&String> = CELL.get();
/// assert!(value.is_some());
/// assert_eq!(value.unwrap().as_str(), "Hello, World!");
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub struct OnceLock<T> {
once: Once,
// Whether or not the value is initialized is tracked by `state_and_queue`.
value: UnsafeCell<MaybeUninit<T>>,
/// `PhantomData` to make sure dropck understands we're dropping T in our Drop impl.
///
/// ```compile_fail,E0597
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// struct A<'a>(&'a str);
///
/// impl<'a> Drop for A<'a> {
/// fn drop(&mut self) {}
/// }
///
/// let cell = OnceLock::new();
/// {
/// let s = String::new();
/// let _ = cell.set(A(&s));
/// }
/// ```
_marker: PhantomData<T>,
}
impl<T> OnceLock<T> {
/// Creates a new empty cell.
#[unstable(feature = "once_cell", issue = "74465")]
#[must_use]
pub const fn new() -> OnceLock<T> {
OnceLock {
once: Once::new(),
value: UnsafeCell::new(MaybeUninit::uninit()),
_marker: PhantomData,
}
}
/// Gets the reference to the underlying value.
///
/// Returns `None` if the cell is empty, or being initialized. This
/// method never blocks.
#[unstable(feature = "once_cell", issue = "74465")]
pub fn get(&self) -> Option<&T> {
if self.is_initialized() {
// Safe b/c checked is_initialized
Some(unsafe { self.get_unchecked() })
} else {
None
}
}
/// Gets the mutable reference to the underlying value.
///
/// Returns `None` if the cell is empty. This method never blocks.
#[unstable(feature = "once_cell", issue = "74465")]
pub fn get_mut(&mut self) -> Option<&mut T> {
if self.is_initialized() {
// Safe b/c checked is_initialized and we have a unique access
Some(unsafe { self.get_unchecked_mut() })
} else {
None
}
}
/// Sets the contents of this cell to `value`.
///
/// May block if another thread is currently attempting to initialize the cell. The cell is
/// guaranteed to contain a value when set returns, though not necessarily the one provided.
///
/// Returns `Ok(())` if the cell's value was set by this call.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// static CELL: OnceLock<i32> = OnceLock::new();
///
/// fn main() {
/// assert!(CELL.get().is_none());
///
/// std::thread::spawn(|| {
/// assert_eq!(CELL.set(92), Ok(()));
/// }).join().unwrap();
///
/// assert_eq!(CELL.set(62), Err(62));
/// assert_eq!(CELL.get(), Some(&92));
/// }
/// ```
#[unstable(feature = "once_cell", issue = "74465")]
pub fn set(&self, value: T) -> Result<(), T> {
let mut value = Some(value);
self.get_or_init(|| value.take().unwrap());
match value {
None => Ok(()),
Some(value) => Err(value),
}
}
/// Gets the contents of the cell, initializing it with `f` if the cell
/// was empty.
///
/// Many threads may call `get_or_init` concurrently with different
/// initializing functions, but it is guaranteed that only one function
/// will be executed.
///
/// # 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`. The
/// exact outcome is unspecified. Current implementation deadlocks, but
/// this may be changed to a panic in the future.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// let cell = OnceLock::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`.
/// The exact outcome is unspecified. Current implementation
/// deadlocks, but this may be changed to a panic in the future.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// let cell = OnceLock::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>,
{
// Fast path check
// NOTE: We need to perform an acquire on the state in this method
// in order to correctly synchronize `LazyLock::force`. This is
// currently done by calling `self.get()`, which in turn calls
// `self.is_initialized()`, which in turn performs the acquire.
if let Some(value) = self.get() {
return Ok(value);
}
self.initialize(f)?;
debug_assert!(self.is_initialized());
// SAFETY: The inner value has been initialized
Ok(unsafe { self.get_unchecked() })
}
/// Internal-only API that gets the contents of the cell, initializing it
/// in two steps with `f` and `g` if the cell was empty.
///
/// `f` is called to construct the value, which is then moved into the cell
/// and given as a (pinned) mutable reference to `g` to finish
/// initialization.
///
/// This allows `g` to inspect an manipulate the value after it has been
/// moved into its final place in the cell, but before the cell is
/// considered initialized.
///
/// # Panics
///
/// If `f` or `g` panics, the panic is propagated to the caller, and the
/// cell remains uninitialized.
///
/// With the current implementation, if `g` panics, the value from `f` will
/// not be dropped. This should probably be fixed if this is ever used for
/// a type where this matters.
///
/// It is an error to reentrantly initialize the cell from `f`. The exact
/// outcome is unspecified. Current implementation deadlocks, but this may
/// be changed to a panic in the future.
pub(crate) fn get_or_init_pin<F, G>(self: Pin<&Self>, f: F, g: G) -> Pin<&T>
where
F: FnOnce() -> T,
G: FnOnce(Pin<&mut T>),
{
if let Some(value) = self.get_ref().get() {
// SAFETY: The inner value was already initialized, and will not be
// moved anymore.
return unsafe { Pin::new_unchecked(value) };
}
let slot = &self.value;
// Ignore poisoning from other threads
// If another thread panics, then we'll be able to run our closure
self.once.call_once_force(|_| {
let value = f();
// SAFETY: We use the Once (self.once) to guarantee unique access
// to the UnsafeCell (slot).
let value: &mut T = unsafe { (&mut *slot.get()).write(value) };
// SAFETY: The value has been written to its final place in
// self.value. We do not to move it anymore, which we promise here
// with a Pin<&mut T>.
g(unsafe { Pin::new_unchecked(value) });
});
// SAFETY: The inner value has been initialized, and will not be moved
// anymore.
unsafe { Pin::new_unchecked(self.get_ref().get_unchecked()) }
}
/// Consumes the `OnceLock`, returning the wrapped value. Returns
/// `None` if the cell was empty.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// let cell: OnceLock<String> = OnceLock::new();
/// assert_eq!(cell.into_inner(), None);
///
/// let cell = OnceLock::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(mut self) -> Option<T> {
self.take()
}
/// Takes the value out of this `OnceLock`, moving it back to an uninitialized state.
///
/// Has no effect and returns `None` if the `OnceLock` hasn't been initialized.
///
/// Safety is guaranteed by requiring a mutable reference.
///
/// # Examples
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// let mut cell: OnceLock<String> = OnceLock::new();
/// assert_eq!(cell.take(), None);
///
/// let mut cell = OnceLock::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> {
if self.is_initialized() {
self.once = Once::new();
// SAFETY: `self.value` is initialized and contains a valid `T`.
// `self.once` is reset, so `is_initialized()` will be false again
// which prevents the value from being read twice.
unsafe { Some((&mut *self.value.get()).assume_init_read()) }
} else {
None
}
}
#[inline]
fn is_initialized(&self) -> bool {
self.once.is_completed()
}
#[cold]
fn initialize<F, E>(&self, f: F) -> Result<(), E>
where
F: FnOnce() -> Result<T, E>,
{
let mut res: Result<(), E> = Ok(());
let slot = &self.value;
// Ignore poisoning from other threads
// If another thread panics, then we'll be able to run our closure
self.once.call_once_force(|p| {
match f() {
Ok(value) => {
unsafe { (&mut *slot.get()).write(value) };
}
Err(e) => {
res = Err(e);
// Treat the underlying `Once` as poisoned since we
// failed to initialize our value. Calls
p.poison();
}
}
});
res
}
/// # Safety
///
/// The value must be initialized
unsafe fn get_unchecked(&self) -> &T {
debug_assert!(self.is_initialized());
(&*self.value.get()).assume_init_ref()
}
/// # Safety
///
/// The value must be initialized
unsafe fn get_unchecked_mut(&mut self) -> &mut T {
debug_assert!(self.is_initialized());
(&mut *self.value.get()).assume_init_mut()
}
}
// Why do we need `T: Send`?
// Thread A creates a `OnceLock` and shares it with
// scoped thread B, which fills the cell, which is
// then destroyed by A. That is, destructor observes
// a sent value.
#[unstable(feature = "once_cell", issue = "74465")]
unsafe impl<T: Sync + Send> Sync for OnceLock<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
unsafe impl<T: Send> Send for OnceLock<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: RefUnwindSafe + UnwindSafe> RefUnwindSafe for OnceLock<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: UnwindSafe> UnwindSafe for OnceLock<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
impl<T> const Default for OnceLock<T> {
/// Creates a new empty cell.
///
/// # Example
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// fn main() {
/// assert_eq!(OnceLock::<()>::new(), OnceLock::default());
/// }
/// ```
fn default() -> OnceLock<T> {
OnceLock::new()
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: fmt::Debug> fmt::Debug for OnceLock<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self.get() {
Some(v) => f.debug_tuple("Once").field(v).finish(),
None => f.write_str("Once(Uninit)"),
}
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: Clone> Clone for OnceLock<T> {
fn clone(&self) -> OnceLock<T> {
let cell = Self::new();
if let Some(value) = self.get() {
match cell.set(value.clone()) {
Ok(()) => (),
Err(_) => unreachable!(),
}
}
cell
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T> From<T> for OnceLock<T> {
/// Create a new cell with its contents set to `value`.
///
/// # Example
///
/// ```
/// #![feature(once_cell)]
///
/// use std::sync::OnceLock;
///
/// # fn main() -> Result<(), i32> {
/// let a = OnceLock::from(3);
/// let b = OnceLock::new();
/// b.set(3)?;
/// assert_eq!(a, b);
/// Ok(())
/// # }
/// ```
fn from(value: T) -> Self {
let cell = Self::new();
match cell.set(value) {
Ok(()) => cell,
Err(_) => unreachable!(),
}
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: PartialEq> PartialEq for OnceLock<T> {
fn eq(&self, other: &OnceLock<T>) -> bool {
self.get() == other.get()
}
}
#[unstable(feature = "once_cell", issue = "74465")]
impl<T: Eq> Eq for OnceLock<T> {}
#[unstable(feature = "once_cell", issue = "74465")]
unsafe impl<#[may_dangle] T> Drop for OnceLock<T> {
fn drop(&mut self) {
if self.is_initialized() {
// SAFETY: The cell is initialized and being dropped, so it can't
// be accessed again. We also don't touch the `T` other than
// dropping it, which validates our usage of #[may_dangle].
unsafe { (&mut *self.value.get()).assume_init_drop() };
}
}
}
#[cfg(test)]
mod tests;

165
library/std/src/lazy/tests.rs → library/std/src/sync/once_lock/tests.rs
View File

@ -1,48 +1,13 @@
use crate::{
lazy::{Lazy, SyncLazy, SyncOnceCell},
panic,
sync::OnceLock,
sync::{
atomic::{AtomicUsize, Ordering::SeqCst},
mpsc::channel,
Mutex,
},
thread,
};
#[test]
fn lazy_default() {
static CALLED: AtomicUsize = AtomicUsize::new(0);
struct Foo(u8);
impl Default for Foo {
fn default() -> Self {
CALLED.fetch_add(1, SeqCst);
Foo(42)
}
}
let lazy: Lazy<Mutex<Foo>> = <_>::default();
assert_eq!(CALLED.load(SeqCst), 0);
assert_eq!(lazy.lock().unwrap().0, 42);
assert_eq!(CALLED.load(SeqCst), 1);
lazy.lock().unwrap().0 = 21;
assert_eq!(lazy.lock().unwrap().0, 21);
assert_eq!(CALLED.load(SeqCst), 1);
}
#[test]
fn lazy_poisoning() {
let x: Lazy<String> = Lazy::new(|| panic!("kaboom"));
for _ in 0..2 {
let res = panic::catch_unwind(panic::AssertUnwindSafe(|| x.len()));
assert!(res.is_err());
}
}
fn spawn_and_wait<R: Send + 'static>(f: impl FnOnce() -> R + Send + 'static) -> R {
thread::spawn(f).join().unwrap()
}
@ -50,7 +15,7 @@ fn spawn_and_wait<R: Send + 'static>(f: impl FnOnce() -> R + Send + 'static) ->
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn sync_once_cell() {
static ONCE_CELL: SyncOnceCell<i32> = SyncOnceCell::new();
static ONCE_CELL: OnceLock<i32> = OnceLock::new();
assert!(ONCE_CELL.get().is_none());
@ -65,7 +30,7 @@ fn sync_once_cell() {
#[test]
fn sync_once_cell_get_mut() {
let mut c = SyncOnceCell::new();
let mut c = OnceLock::new();
assert!(c.get_mut().is_none());
c.set(90).unwrap();
*c.get_mut().unwrap() += 2;
@ -74,7 +39,7 @@ fn sync_once_cell_get_mut() {
#[test]
fn sync_once_cell_get_unchecked() {
let c = SyncOnceCell::new();
let c = OnceLock::new();
c.set(92).unwrap();
unsafe {
assert_eq!(c.get_unchecked(), &92);
@ -92,7 +57,7 @@ fn sync_once_cell_drop() {
}
}
let x = SyncOnceCell::new();
let x = OnceLock::new();
spawn_and_wait(move || {
x.get_or_init(|| Dropper);
assert_eq!(DROP_CNT.load(SeqCst), 0);
@ -104,13 +69,13 @@ fn sync_once_cell_drop() {
#[test]
fn sync_once_cell_drop_empty() {
let x = SyncOnceCell::<String>::new();
let x = OnceLock::<String>::new();
drop(x);
}
#[test]
fn clone() {
let s = SyncOnceCell::new();
let s = OnceLock::new();
let c = s.clone();
assert!(c.get().is_none());
@ -121,7 +86,7 @@ fn clone() {
#[test]
fn get_or_try_init() {
let cell: SyncOnceCell<String> = SyncOnceCell::new();
let cell: OnceLock<String> = OnceLock::new();
assert!(cell.get().is_none());
let res = panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
@ -137,122 +102,32 @@ fn get_or_try_init() {
#[test]
fn from_impl() {
assert_eq!(SyncOnceCell::from("value").get(), Some(&"value"));
assert_ne!(SyncOnceCell::from("foo").get(), Some(&"bar"));
assert_eq!(OnceLock::from("value").get(), Some(&"value"));
assert_ne!(OnceLock::from("foo").get(), Some(&"bar"));
}
#[test]
fn partialeq_impl() {
assert!(SyncOnceCell::from("value") == SyncOnceCell::from("value"));
assert!(SyncOnceCell::from("foo") != SyncOnceCell::from("bar"));
assert!(OnceLock::from("value") == OnceLock::from("value"));
assert!(OnceLock::from("foo") != OnceLock::from("bar"));
assert!(SyncOnceCell::<String>::new() == SyncOnceCell::new());
assert!(SyncOnceCell::<String>::new() != SyncOnceCell::from("value".to_owned()));
assert!(OnceLock::<String>::new() == OnceLock::new());
assert!(OnceLock::<String>::new() != OnceLock::from("value".to_owned()));
}
#[test]
fn into_inner() {
let cell: SyncOnceCell<String> = SyncOnceCell::new();
let cell: OnceLock<String> = OnceLock::new();
assert_eq!(cell.into_inner(), None);
let cell = SyncOnceCell::new();
let cell = OnceLock::new();
cell.set("hello".to_string()).unwrap();
assert_eq!(cell.into_inner(), Some("hello".to_string()));
}
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn sync_lazy_new() {
static CALLED: AtomicUsize = AtomicUsize::new(0);
static SYNC_LAZY: SyncLazy<i32> = SyncLazy::new(|| {
CALLED.fetch_add(1, SeqCst);
92
});
assert_eq!(CALLED.load(SeqCst), 0);
spawn_and_wait(|| {
let y = *SYNC_LAZY - 30;
assert_eq!(y, 62);
assert_eq!(CALLED.load(SeqCst), 1);
});
let y = *SYNC_LAZY - 30;
assert_eq!(y, 62);
assert_eq!(CALLED.load(SeqCst), 1);
}
#[test]
fn sync_lazy_default() {
static CALLED: AtomicUsize = AtomicUsize::new(0);
struct Foo(u8);
impl Default for Foo {
fn default() -> Self {
CALLED.fetch_add(1, SeqCst);
Foo(42)
}
}
let lazy: SyncLazy<Mutex<Foo>> = <_>::default();
assert_eq!(CALLED.load(SeqCst), 0);
assert_eq!(lazy.lock().unwrap().0, 42);
assert_eq!(CALLED.load(SeqCst), 1);
lazy.lock().unwrap().0 = 21;
assert_eq!(lazy.lock().unwrap().0, 21);
assert_eq!(CALLED.load(SeqCst), 1);
}
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn static_sync_lazy() {
static XS: SyncLazy<Vec<i32>> = SyncLazy::new(|| {
let mut xs = Vec::new();
xs.push(1);
xs.push(2);
xs.push(3);
xs
});
spawn_and_wait(|| {
assert_eq!(&*XS, &vec![1, 2, 3]);
});
assert_eq!(&*XS, &vec![1, 2, 3]);
}
#[test]
fn static_sync_lazy_via_fn() {
fn xs() -> &'static Vec<i32> {
static XS: SyncOnceCell<Vec<i32>> = SyncOnceCell::new();
XS.get_or_init(|| {
let mut xs = Vec::new();
xs.push(1);
xs.push(2);
xs.push(3);
xs
})
}
assert_eq!(xs(), &vec![1, 2, 3]);
}
#[test]
fn sync_lazy_poisoning() {
let x: SyncLazy<String> = SyncLazy::new(|| panic!("kaboom"));
for _ in 0..2 {
let res = panic::catch_unwind(|| x.len());
assert!(res.is_err());
}
}
#[test]
fn is_sync_send() {
fn assert_traits<T: Send + Sync>() {}
assert_traits::<SyncOnceCell<String>>();
assert_traits::<SyncLazy<String>>();
assert_traits::<OnceLock<String>>();
}
#[test]
@ -261,7 +136,7 @@ fn eval_once_macro() {
(|| -> $ty:ty {
$($body:tt)*
}) => {{
static ONCE_CELL: SyncOnceCell<$ty> = SyncOnceCell::new();
static ONCE_CELL: OnceLock<$ty> = OnceLock::new();
fn init() -> $ty {
$($body)*
}
@ -285,7 +160,7 @@ fn eval_once_macro() {
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn sync_once_cell_does_not_leak_partially_constructed_boxes() {
static ONCE_CELL: SyncOnceCell<String> = SyncOnceCell::new();
static ONCE_CELL: OnceLock<String> = OnceLock::new();
let n_readers = 10;
let n_writers = 3;
@ -320,7 +195,7 @@ fn sync_once_cell_does_not_leak_partially_constructed_boxes() {
#[test]
fn dropck() {
let cell = SyncOnceCell::new();
let cell = OnceLock::new();
{
let s = String::new();
cell.set(&s).unwrap();

4
library/std/src/sys/windows/net.rs
View File

@ -2,13 +2,13 @@
use crate::cmp;
use crate::io::{self, IoSlice, IoSliceMut, Read};
use crate::lazy::SyncOnceCell;
use crate::mem;
use crate::net::{Shutdown, SocketAddr};
use crate::os::windows::io::{
AsRawSocket, AsSocket, BorrowedSocket, FromRawSocket, IntoRawSocket, OwnedSocket, RawSocket,
};
use crate::ptr;
use crate::sync::OnceLock;
use crate::sys;
use crate::sys::c;
use crate::sys_common::net;
@ -29,7 +29,7 @@ pub mod netc {
pub struct Socket(OwnedSocket);
static WSA_CLEANUP: SyncOnceCell<unsafe extern "system" fn() -> i32> = SyncOnceCell::new();
static WSA_CLEANUP: OnceLock<unsafe extern "system" fn() -> i32> = OnceLock::new();
/// Checks whether the Windows socket interface has been started already, and
/// if not, starts it.

4
library/std/src/sys/windows/rand.rs
View File

@ -1,6 +1,6 @@
use crate::io;
use crate::lazy;
use crate::mem;
use crate::sync;
use crate::sys::c;
/// The kinds of HashMap RNG that may be available
@ -28,7 +28,7 @@ fn get_hashmap_rng() -> HashMapRng {
// Assume that if the preferred RNG is broken the first time we use it, it likely means
// that: the DLL has failed to load, there is no point to calling it over-and-over again,
// and we should cache the result
static VALUE: lazy::SyncOnceCell<HashMapRng> = lazy::SyncOnceCell::new();
static VALUE: sync::OnceLock<HashMapRng> = sync::OnceLock::new();
*VALUE.get_or_init(choose_hashmap_rng)
}

2
src/librustdoc/clean/types.rs
View File

@ -1,10 +1,10 @@
use std::cell::RefCell;
use std::default::Default;
use std::hash::Hash;
use std::lazy::SyncOnceCell as OnceCell;
use std::path::PathBuf;
use std::rc::Rc;
use std::sync::Arc;
use std::sync::OnceLock as OnceCell;
use std::{cmp, fmt, iter};
use arrayvec::ArrayVec;

6
src/librustdoc/core.rs
View File

@ -21,9 +21,9 @@ use rustc_span::symbol::sym;
use rustc_span::{source_map, Span, Symbol};
use std::cell::RefCell;
use std::lazy::SyncLazy;
use std::mem;
use std::rc::Rc;
use std::sync::LazyLock;
use crate::clean::inline::build_external_trait;
use crate::clean::{self, ItemId, TraitWithExtraInfo};
@ -293,8 +293,8 @@ pub(crate) fn create_config(
providers.typeck_item_bodies = |_, _| {};
// hack so that `used_trait_imports` won't try to call typeck
providers.used_trait_imports = |_, _| {
static EMPTY_SET: SyncLazy<FxHashSet<LocalDefId>> =
SyncLazy::new(FxHashSet::default);
static EMPTY_SET: LazyLock<FxHashSet<LocalDefId>> =
LazyLock::new(FxHashSet::default);
&EMPTY_SET
};
// In case typeck does end up being called, don't ICE in case there were name resolution errors

2
src/librustdoc/html/render/write_shared.rs
View File

@ -3,9 +3,9 @@ use std::fmt::Write;
use std::fs::{self, File};
use std::io::prelude::*;
use std::io::{self, BufReader};
use std::lazy::SyncLazy as Lazy;
use std::path::{Component, Path, PathBuf};
use std::rc::Rc;
use std::sync::LazyLock as Lazy;
use itertools::Itertools;
use rustc_data_structures::flock;

2
src/librustdoc/lint.rs
View File

@ -3,7 +3,7 @@ use rustc_lint::LintStore;
use rustc_lint_defs::{declare_tool_lint, Lint, LintId};
use rustc_session::{lint, Session};
use std::lazy::SyncLazy as Lazy;
use std::sync::LazyLock as Lazy;
/// This function is used to setup the lint initialization. By default, in rustdoc, everything
/// is "allowed". Depending if we run in test mode or not, we want some of them to be at their

4
src/librustdoc/passes/bare_urls.rs
View File

@ -9,8 +9,8 @@ use core::ops::Range;
use pulldown_cmark::{Event, Parser, Tag};
use regex::Regex;
use rustc_errors::Applicability;
use std::lazy::SyncLazy;
use std::mem;
use std::sync::LazyLock;
pub(crate) const CHECK_BARE_URLS: Pass = Pass {
name: "check-bare-urls",
@ -18,7 +18,7 @@ pub(crate) const CHECK_BARE_URLS: Pass = Pass {
description: "detects URLs that are not hyperlinks",
};
static URL_REGEX: SyncLazy<Regex> = SyncLazy::new(|| {
static URL_REGEX: LazyLock<Regex> = LazyLock::new(|| {
Regex::new(concat!(
r"https?://", // url scheme
r"([-a-zA-Z0-9@:%._\+~#=]{2,256}\.)+", // one or more subdomains

8
src/test/run-make/libtest-thread-limit/test.rs
View File

@ -1,8 +1,12 @@
#![feature(once_cell)]
use std::{io::ErrorKind, lazy::SyncOnceCell, thread::{self, Builder, ThreadId}};
use std::{
io::ErrorKind,
sync::OnceLock,
thread::{self, Builder, ThreadId},
};
static THREAD_ID: SyncOnceCell<ThreadId> = SyncOnceCell::new();
static THREAD_ID: OnceLock<ThreadId> = OnceLock::new();
#[test]
fn spawn_thread_would_block() {

6
src/tools/clippy/clippy_dev/src/bless.rs
View File

@ -4,12 +4,12 @@
use crate::cargo_clippy_path;
use std::ffi::OsStr;
use std::fs;
use std::lazy::SyncLazy;
use std::path::{Path, PathBuf};
use std::sync::LazyLock;
use walkdir::{DirEntry, WalkDir};
static CLIPPY_BUILD_TIME: SyncLazy<Option<std::time::SystemTime>> =
SyncLazy::new(|| cargo_clippy_path().metadata().ok()?.modified().ok());
static CLIPPY_BUILD_TIME: LazyLock<Option<std::time::SystemTime>> =
LazyLock::new(|| cargo_clippy_path().metadata().ok()?.modified().ok());
/// # Panics
///

4
src/tools/clippy/clippy_utils/src/lib.rs
View File

@ -64,7 +64,7 @@ pub use self::hir_utils::{
use std::collections::hash_map::Entry;
use std::hash::BuildHasherDefault;
use std::lazy::SyncOnceCell;
use std::sync::OnceLock;
use std::sync::{Mutex, MutexGuard};
use if_chain::if_chain;
@ -2080,7 +2080,7 @@ pub fn is_hir_ty_cfg_dependant(cx: &LateContext<'_>, ty: &hir::Ty<'_>) -> bool {
false
}
static TEST_ITEM_NAMES_CACHE: SyncOnceCell<Mutex<FxHashMap<LocalDefId, Vec<Symbol>>>> = SyncOnceCell::new();
static TEST_ITEM_NAMES_CACHE: OnceLock<Mutex<FxHashMap<LocalDefId, Vec<Symbol>>>> = OnceLock::new();
fn with_test_item_names<'tcx>(tcx: TyCtxt<'tcx>, module: LocalDefId, f: impl Fn(&[Symbol]) -> bool) -> bool {
let cache = TEST_ITEM_NAMES_CACHE.get_or_init(|| Mutex::new(FxHashMap::default()));

6
src/tools/clippy/src/driver.rs
View File

@ -21,11 +21,11 @@ use rustc_tools_util::VersionInfo;
use std::borrow::Cow;
use std::env;
use std::lazy::SyncLazy;
use std::ops::Deref;
use std::panic;
use std::path::{Path, PathBuf};
use std::process::{exit, Command};
use std::sync::LazyLock;
/// If a command-line option matches `find_arg`, then apply the predicate `pred` on its value. If
/// true, then return it. The parameter is assumed to be either `--arg=value` or `--arg value`.
@ -152,7 +152,7 @@ You can use tool lints to allow or deny lints from your code, eg.:
const BUG_REPORT_URL: &str = "https://github.com/rust-lang/rust-clippy/issues/new";
static ICE_HOOK: SyncLazy<Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send + 'static>> = SyncLazy::new(|| {
static ICE_HOOK: LazyLock<Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send + 'static>> = LazyLock::new(|| {
let hook = panic::take_hook();
panic::set_hook(Box::new(|info| report_clippy_ice(info, BUG_REPORT_URL)));
hook
@ -219,7 +219,7 @@ fn toolchain_path(home: Option<String>, toolchain: Option<String>) -> Option<Pat
#[allow(clippy::too_many_lines)]
pub fn main() {
rustc_driver::init_rustc_env_logger();
SyncLazy::force(&ICE_HOOK);
LazyLock::force(&ICE_HOOK);
exit(rustc_driver::catch_with_exit_code(move || {
let mut orig_args: Vec<String> = env::args().collect();

4
src/tools/clippy/tests/compile-test.rs
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@ -12,8 +12,8 @@ use std::env::{self, remove_var, set_var, var_os};
use std::ffi::{OsStr, OsString};
use std::fs;
use std::io;
use std::lazy::SyncLazy;
use std::path::{Path, PathBuf};
use std::sync::LazyLock;
use test_utils::IS_RUSTC_TEST_SUITE;
mod test_utils;
@ -69,7 +69,7 @@ extern crate tokio;
/// dependencies must be added to Cargo.toml at the project root. Test
/// dependencies that are not *directly* used by this test module require an
/// `extern crate` declaration.
static EXTERN_FLAGS: SyncLazy<String> = SyncLazy::new(|| {
static EXTERN_FLAGS: LazyLock<String> = LazyLock::new(|| {
let current_exe_depinfo = {
let mut path = env::current_exe().unwrap();
path.set_extension("d");

4
src/tools/clippy/tests/test_utils/mod.rs
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@ -1,9 +1,9 @@
#![allow(dead_code)] // see https://github.com/rust-lang/rust/issues/46379
use std::lazy::SyncLazy;
use std::path::PathBuf;
use std::sync::LazyLock;
pub static CARGO_CLIPPY_PATH: SyncLazy<PathBuf> = SyncLazy::new(|| {
pub static CARGO_CLIPPY_PATH: LazyLock<PathBuf> = LazyLock::new(|| {
let mut path = std::env::current_exe().unwrap();
assert!(path.pop()); // deps
path.set_file_name("cargo-clippy");