replace once_cell::sync::OnceCell with std OnceLock

src/bootstrap/src/core/builder.rs

@@ -10,6 +10,7 @@ use std::io::{BufRead, BufReader};
 use std::ops::Deref;
 use std::path::{Path, PathBuf};
 use std::process::Command;
+use std::sync::OnceLock;
 use std::time::{Duration, Instant};
 
 use crate::core::build_steps::llvm;
@@ -25,12 +26,10 @@ use crate::EXTRA_CHECK_CFGS;
 use crate::{Build, CLang, DocTests, GitRepo, Mode};
 
 pub use crate::Compiler;
-// FIXME:
-// - use std::lazy for `Lazy`
-// - use std::cell for `OnceCell`
-// Once they get stabilized and reach beta.
+
 use clap::ValueEnum;
-use once_cell::sync::{Lazy, OnceCell};
+// FIXME: replace with std::lazy after it gets stabilized and reaches beta
+use once_cell::sync::Lazy;
 
 #[cfg(test)]
 #[path = "../tests/builder.rs"]
@@ -496,7 +495,7 @@ impl<'a> ShouldRun<'a> {
     ///
     /// [`path`]: ShouldRun::path
     pub fn paths(mut self, paths: &[&str]) -> Self {
-        static SUBMODULES_PATHS: OnceCell<Vec<String>> = OnceCell::new();
+        static SUBMODULES_PATHS: OnceLock<Vec<String>> = OnceLock::new();
 
         let init_submodules_paths = |src: &PathBuf| {
             let file = File::open(src.join(".gitmodules")).unwrap();

src/bootstrap/src/core/config/config.rs

@@ -17,6 +17,7 @@ use std::io::IsTerminal;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::str::FromStr;
+use std::sync::OnceLock;
 
 use crate::core::build_steps::compile::CODEGEN_BACKEND_PREFIX;
 use crate::core::build_steps::llvm;
@@ -25,7 +26,6 @@ use crate::utils::cache::{Interned, INTERNER};
 use crate::utils::channel::{self, GitInfo};
 use crate::utils::helpers::{exe, output, t};
 use build_helper::exit;
-use once_cell::sync::OnceCell;
 use semver::Version;
 use serde::{Deserialize, Deserializer};
 use serde_derive::Deserialize;
@@ -1907,7 +1907,7 @@ impl Config {
     }
 
     pub(crate) fn download_rustc_commit(&self) -> Option<&str> {
-        static DOWNLOAD_RUSTC: OnceCell<Option<String>> = OnceCell::new();
+        static DOWNLOAD_RUSTC: OnceLock<Option<String>> = OnceLock::new();
         if self.dry_run() && DOWNLOAD_RUSTC.get().is_none() {
             // avoid trying to actually download the commit
             return self.download_rustc_commit.as_deref();

src/bootstrap/src/core/download.rs

@@ -5,18 +5,18 @@ use std::{
     io::{BufRead, BufReader, BufWriter, ErrorKind, Write},
     path::{Path, PathBuf},
     process::{Command, Stdio},
+    sync::OnceLock,
 };
 
 use build_helper::ci::CiEnv;
-use once_cell::sync::OnceCell;
 use xz2::bufread::XzDecoder;
 
 use crate::core::build_steps::llvm::detect_llvm_sha;
 use crate::core::config::RustfmtMetadata;
 use crate::utils::helpers::{check_run, exe, program_out_of_date};
 use crate::{t, Config};
 
-static SHOULD_FIX_BINS_AND_DYLIBS: OnceCell<bool> = OnceCell::new();
+static SHOULD_FIX_BINS_AND_DYLIBS: OnceLock<bool> = OnceLock::new();
 
 /// `Config::try_run` wrapper for this module to avoid warnings on `try_run`, since we don't have access to a `builder` yet.
 fn try_run(config: &Config, cmd: &mut Command) -> Result<(), ()> {
@@ -131,7 +131,7 @@ impl Config {
         println!("attempting to patch {}", fname.display());
 
         // Only build `.nix-deps` once.
-        static NIX_DEPS_DIR: OnceCell<PathBuf> = OnceCell::new();
+        static NIX_DEPS_DIR: OnceLock<PathBuf> = OnceLock::new();
         let mut nix_build_succeeded = true;
         let nix_deps_dir = NIX_DEPS_DIR.get_or_init(|| {
             // Run `nix-build` to "build" each dependency (which will likely reuse

src/bootstrap/src/lib.rs

@@ -25,12 +25,12 @@ use std::io;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Output, Stdio};
 use std::str;
+use std::sync::OnceLock;
 
 use build_helper::ci::{gha, CiEnv};
 use build_helper::exit;
 use build_helper::util::fail;
 use filetime::FileTime;
-use once_cell::sync::OnceCell;
 use sha2::digest::Digest;
 use termcolor::{ColorChoice, StandardStream, WriteColor};
 use utils::channel::GitInfo;
@@ -906,7 +906,7 @@ impl Build {
 
     /// Returns the sysroot of the snapshot compiler.
     fn rustc_snapshot_sysroot(&self) -> &Path {
-        static SYSROOT_CACHE: OnceCell<PathBuf> = once_cell::sync::OnceCell::new();
+        static SYSROOT_CACHE: OnceLock<PathBuf> = OnceLock::new();
         SYSROOT_CACHE.get_or_init(|| {
             let mut rustc = Command::new(&self.initial_rustc);
             rustc.args(&["--print", "sysroot"]);

src/bootstrap/src/utils/helpers.rs

@@ -11,11 +11,11 @@ use std::io;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 use std::str;
+use std::sync::OnceLock;
 use std::time::{Instant, SystemTime, UNIX_EPOCH};
 
 use crate::core::builder::Builder;
 use crate::core::config::{Config, TargetSelection};
-use crate::OnceCell;
 
 pub use crate::utils::dylib::{dylib_path, dylib_path_var};
 
@@ -444,7 +444,7 @@ pub fn get_clang_cl_resource_dir(clang_cl_path: &str) -> PathBuf {
 }
 
 pub fn lld_flag_no_threads(is_windows: bool) -> &'static str {
-    static LLD_NO_THREADS: OnceCell<(&'static str, &'static str)> = OnceCell::new();
+    static LLD_NO_THREADS: OnceLock<(&'static str, &'static str)> = OnceLock::new();
     let (windows, other) = LLD_NO_THREADS.get_or_init(|| {
         let out = output(Command::new("lld").arg("-flavor").arg("ld").arg("--version"));
         let newer = match (out.find(char::is_numeric), out.find('.')) {