feat: loom support

.gitignore

@@ -2,3 +2,4 @@
 **/*.rs.bk
 Cargo.lock
 .vscode/
+.zed/

Cargo.toml

@@ -21,8 +21,12 @@ current_thread_id = []
 nightly = ["current_thread_id"]
 
 [dependencies]
+cfg-if = "1.0.0"
 futures-core = { version = "0.3", optional = true }
 
+[target.'cfg(loom)'.dependencies]
+loom = "0.7"
+
 [dev-dependencies]
 futures-executor = "0.3"
 futures-util = "0.3"
@@ -31,3 +35,6 @@ futures-util = "0.3"
 all-features = true
 # Needed to add "Available on crate feature `futures` only." messages to docs
 rustdoc-args = ["--cfg", "docsrs"]
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(loom)'] }

src/lib.rs

@@ -82,40 +82,42 @@
 //! [`Stream`]: futures_core::Stream
 // To build docs locally use `RUSTDOCFLAGS="--cfg docsrs" cargo doc --open --all-features`
 #![cfg_attr(docsrs, feature(doc_cfg))]
-#![cfg_attr(feature = "current_thread_id", feature(current_thread_id))]
+#![cfg_attr(
+    all(not(loom), feature = "current_thread_id"),
+    feature(current_thread_id)
+)]
 #![warn(missing_docs)]
 
 #[cfg(feature = "futures")]
 #[cfg_attr(docsrs, doc(cfg(feature = "futures")))]
 mod futures;
 
-#[cfg(feature = "current_thread_id")]
-use std::thread::current_id;
 use std::{
     fmt,
     mem::{self, ManuallyDrop},
     pin::Pin,
-    thread::{self, ThreadId},
 };
 
-#[cfg(not(feature = "current_thread_id"))]
-mod imp {
-    use std::{
-        cell::Cell,
-        thread::{self, ThreadId},
-    };
-    thread_local! {
-        static THREAD_ID: Cell<ThreadId> = Cell::new(thread::current().id());
-    }
+cfg_if::cfg_if! {
+    if #[cfg(any(loom, not(feature = "current_thread_id")))] {
+        #[cfg(loom)]
+        use loom::{thread_local, cell::Cell, thread::{self, ThreadId}};
+        #[cfg(not(loom))]
+        use std::{thread_local, cell::Cell, thread::{self, ThreadId}};
 
-    pub fn current_id() -> ThreadId {
-        THREAD_ID.get()
+        thread_local! {
+            static THREAD_ID: Cell<ThreadId> = Cell::new(thread::current().id());
+        }
+
+        /// Get the current [`ThreadId`].
+        pub(crate) fn current_id() -> ThreadId {
+            THREAD_ID.with(|id| id.get())
+        }
+    } else {
+        use std::thread::{self, current_id, ThreadId};
     }
 }
 
-#[cfg(not(feature = "current_thread_id"))]
-use imp::current_id;
-
 /// A wrapper which allows you to move around non-[`Send`]-types between
 /// threads, as long as you access the contained value only from within the
 /// original thread and make sure that it is dropped from within the original