rt: move task::Id into its own file (#5327)

This is a minor internal cleanup.

.github/workflows/ci.yml

@@ -348,10 +348,14 @@ jobs:
       # release.
       - name: "check -p tokio --all-features"
         run: cargo check -p tokio --all-features
+        env:
+          RUSTFLAGS: "" # remove -Dwarnings
       - name: "pin once_cell version"
         run: cargo update -p once_cell --precise 1.14.0
       - name: "check --workspace --all-features"
         run: cargo check --workspace --all-features
+        env:
+          RUSTFLAGS: "" # remove -Dwarnings
 
   minimal-versions:
     name: minimal-versions

tokio/src/runtime/task/id.rs

@@ -0,0 +1,87 @@
+use crate::runtime::context;
+
+use std::fmt;
+
+/// An opaque ID that uniquely identifies a task relative to all other currently
+/// running tasks.
+///
+/// # Notes
+///
+/// - Task IDs are unique relative to other *currently running* tasks. When a
+///   task completes, the same ID may be used for another task.
+/// - Task IDs are *not* sequential, and do not indicate the order in which
+///   tasks are spawned, what runtime a task is spawned on, or any other data.
+/// - The task ID of the currently running task can be obtained from inside the
+///   task via the [`task::try_id()`](crate::task::try_id()) and
+///   [`task::id()`](crate::task::id()) functions and from outside the task via
+///   the [`JoinHandle::id()`](crate::task::JoinHandle::id()) function.
+///
+/// **Note**: This is an [unstable API][unstable]. The public API of this type
+/// may break in 1.x releases. See [the documentation on unstable
+/// features][unstable] for details.
+///
+/// [unstable]: crate#unstable-features
+#[cfg_attr(docsrs, doc(cfg(all(feature = "rt", tokio_unstable))))]
+#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
+#[derive(Clone, Copy, Debug, Hash, Eq, PartialEq)]
+pub struct Id(u64);
+
+/// Returns the [`Id`] of the currently running task.
+///
+/// # Panics
+///
+/// This function panics if called from outside a task. Please note that calls
+/// to `block_on` do not have task IDs, so the method will panic if called from
+/// within a call to `block_on`. For a version of this function that doesn't
+/// panic, see [`task::try_id()`](crate::runtime::task::try_id()).
+///
+/// **Note**: This is an [unstable API][unstable]. The public API of this type
+/// may break in 1.x releases. See [the documentation on unstable
+/// features][unstable] for details.
+///
+/// [task ID]: crate::task::Id
+/// [unstable]: crate#unstable-features
+#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
+#[track_caller]
+pub fn id() -> Id {
+    context::current_task_id().expect("Can't get a task id when not inside a task")
+}
+
+/// Returns the [`Id`] of the currently running task, or `None` if called outside
+/// of a task.
+///
+/// This function is similar to  [`task::id()`](crate::runtime::task::id()), except
+/// that it returns `None` rather than panicking if called outside of a task
+/// context.
+///
+/// **Note**: This is an [unstable API][unstable]. The public API of this type
+/// may break in 1.x releases. See [the documentation on unstable
+/// features][unstable] for details.
+///
+/// [task ID]: crate::task::Id
+/// [unstable]: crate#unstable-features
+#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
+#[track_caller]
+pub fn try_id() -> Option<Id> {
+    context::current_task_id()
+}
+
+impl fmt::Display for Id {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl Id {
+    pub(crate) fn next() -> Self {
+        use crate::loom::sync::atomic::{Ordering::Relaxed, StaticAtomicU64};
+
+        static NEXT_ID: StaticAtomicU64 = StaticAtomicU64::new(1);
+
+        Self(NEXT_ID.fetch_add(1, Relaxed))
+    }
+
+    pub(crate) fn as_u64(&self) -> u64 {
+        self.0
+    }
+}

tokio/src/runtime/task/mod.rs

@@ -168,19 +168,20 @@
 // unstable. This should be removed once `JoinSet` is stabilized.
 #![cfg_attr(not(tokio_unstable), allow(dead_code))]
 
-use crate::runtime::context;
-
 mod core;
 use self::core::Cell;
 use self::core::Header;
 
 mod error;
-#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
 pub use self::error::JoinError;
 
 mod harness;
 use self::harness::Harness;
 
+mod id;
+#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
+pub use id::{id, try_id, Id};
+
 cfg_rt_multi_thread! {
     mod inject;
     pub(super) use self::inject::Inject;
@@ -191,10 +192,8 @@ mod abort;
 mod join;
 
 #[cfg(feature = "rt")]
-#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
 pub use self::abort::AbortHandle;
 
-#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
 pub use self::join::JoinHandle;
 
 mod list;
@@ -215,70 +214,6 @@ use std::marker::PhantomData;
 use std::ptr::NonNull;
 use std::{fmt, mem};
 
-/// An opaque ID that uniquely identifies a task relative to all other currently
-/// running tasks.
-///
-/// # Notes
-///
-/// - Task IDs are unique relative to other *currently running* tasks. When a
-///   task completes, the same ID may be used for another task.
-/// - Task IDs are *not* sequential, and do not indicate the order in which
-///   tasks are spawned, what runtime a task is spawned on, or any other data.
-/// - The task ID of the currently running task can be obtained from inside the
-///   task via the [`task::try_id()`](crate::task::try_id()) and
-///   [`task::id()`](crate::task::id()) functions and from outside the task via
-///   the [`JoinHandle::id()`](crate::task::JoinHandle::id()) function.
-///
-/// **Note**: This is an [unstable API][unstable]. The public API of this type
-/// may break in 1.x releases. See [the documentation on unstable
-/// features][unstable] for details.
-///
-/// [unstable]: crate#unstable-features
-#[cfg_attr(docsrs, doc(cfg(all(feature = "rt", tokio_unstable))))]
-#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
-#[derive(Clone, Copy, Debug, Hash, Eq, PartialEq)]
-pub struct Id(u64);
-
-/// Returns the [`Id`] of the currently running task.
-///
-/// # Panics
-///
-/// This function panics if called from outside a task. Please note that calls
-/// to `block_on` do not have task IDs, so the method will panic if called from
-/// within a call to `block_on`. For a version of this function that doesn't
-/// panic, see [`task::try_id()`](crate::runtime::task::try_id()).
-///
-/// **Note**: This is an [unstable API][unstable]. The public API of this type
-/// may break in 1.x releases. See [the documentation on unstable
-/// features][unstable] for details.
-///
-/// [task ID]: crate::task::Id
-/// [unstable]: crate#unstable-features
-#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
-#[track_caller]
-pub fn id() -> Id {
-    context::current_task_id().expect("Can't get a task id when not inside a task")
-}
-
-/// Returns the [`Id`] of the currently running task, or `None` if called outside
-/// of a task.
-///
-/// This function is similar to  [`task::id()`](crate::runtime::task::id()), except
-/// that it returns `None` rather than panicking if called outside of a task
-/// context.
-///
-/// **Note**: This is an [unstable API][unstable]. The public API of this type
-/// may break in 1.x releases. See [the documentation on unstable
-/// features][unstable] for details.
-///
-/// [task ID]: crate::task::Id
-/// [unstable]: crate#unstable-features
-#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
-#[track_caller]
-pub fn try_id() -> Option<Id> {
-    context::current_task_id()
-}
-
 /// An owned handle to the task, tracked by ref count.
 #[repr(transparent)]
 pub(crate) struct Task<S: 'static> {
@@ -554,23 +489,3 @@ unsafe impl<S> linked_list::Link for Task<S> {
         self::core::Trailer::addr_of_owned(Header::get_trailer(target))
     }
 }
-
-impl fmt::Display for Id {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.0.fmt(f)
-    }
-}
-
-impl Id {
-    pub(crate) fn next() -> Self {
-        use crate::loom::sync::atomic::{Ordering::Relaxed, StaticAtomicU64};
-
-        static NEXT_ID: StaticAtomicU64 = StaticAtomicU64::new(1);
-
-        Self(NEXT_ID.fetch_add(1, Relaxed))
-    }
-
-    pub(crate) fn as_u64(&self) -> u64 {
-        self.0
-    }
-}