Rollup merge of rust-lang#132869 - lolbinarycat:library-fix-too_long_first_doc_paragraph, r=tgross35

split up the first paragraph of doc comments for better summaries

used `./x clippy -Aclippy::all '-Wclippy::too_long_first_doc_paragraph' library/core library/alloc` to find these issues.

Author: matthiaskrgr

alloc/src/rc.rs

@@ -2932,7 +2932,9 @@ impl<T, I: iter::TrustedLen<Item = T>> ToRcSlice<T> for I {
 }
 
 /// `Weak` is a version of [`Rc`] that holds a non-owning reference to the
-/// managed allocation. The allocation is accessed by calling [`upgrade`] on the `Weak`
+/// managed allocation.
+///
+/// The allocation is accessed by calling [`upgrade`] on the `Weak`
 /// pointer, which returns an <code>[Option]<[Rc]\<T>></code>.
 ///
 /// Since a `Weak` reference does not count towards ownership, it will not

alloc/src/sync.rs

@@ -291,7 +291,9 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
 }
 
 /// `Weak` is a version of [`Arc`] that holds a non-owning reference to the
-/// managed allocation. The allocation is accessed by calling [`upgrade`] on the `Weak`
+/// managed allocation.
+///
+/// The allocation is accessed by calling [`upgrade`] on the `Weak`
 /// pointer, which returns an <code>[Option]<[Arc]\<T>></code>.
 ///
 /// Since a `Weak` reference does not count towards ownership, it will not

alloc/src/task.rs

@@ -176,9 +176,11 @@ fn raw_waker<W: Wake + Send + Sync + 'static>(waker: Arc<W>) -> RawWaker {
     )
 }
 
-/// An analogous trait to `Wake` but used to construct a `LocalWaker`. This API
-/// works in exactly the same way as `Wake`, except that it uses an `Rc` instead
-/// of an `Arc`, and the result is a `LocalWaker` instead of a `Waker`.
+/// An analogous trait to `Wake` but used to construct a `LocalWaker`.
+///
+/// This API works in exactly the same way as `Wake`,
+/// except that it uses an `Rc` instead of an `Arc`,
+/// and the result is a `LocalWaker` instead of a `Waker`.
 ///
 /// The benefits of using `LocalWaker` over `Waker` are that it allows the local waker
 /// to hold data that does not implement `Send` and `Sync`. Additionally, it saves calls

std/src/sync/mpmc/mod.rs

@@ -153,6 +153,7 @@ use crate::panic::{RefUnwindSafe, UnwindSafe};
 use crate::time::{Duration, Instant};
 
 /// Creates a new asynchronous channel, returning the sender/receiver halves.
+///
 /// All data sent on the [`Sender`] will become available on the [`Receiver`] in
 /// the same order as it was sent, and no [`send`] will block the calling thread
 /// (this channel has an "infinite buffer", unlike [`sync_channel`], which will
@@ -201,6 +202,7 @@ pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
 }
 
 /// Creates a new synchronous, bounded channel.
+///
 /// All data sent on the [`Sender`] will become available on the [`Receiver`]
 /// in the same order as it was sent. Like asynchronous [`channel`]s, the
 /// [`Receiver`] will block until a message becomes available. `sync_channel`

std/src/sync/mpsc/mod.rs

@@ -483,6 +483,7 @@ pub enum TrySendError<T> {
 }
 
 /// Creates a new asynchronous channel, returning the sender/receiver halves.
+///
 /// All data sent on the [`Sender`] will become available on the [`Receiver`] in
 /// the same order as it was sent, and no [`send`] will block the calling thread
 /// (this channel has an "infinite buffer", unlike [`sync_channel`], which will
@@ -527,6 +528,7 @@ pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
 }
 
 /// Creates a new synchronous, bounded channel.
+///
 /// All data sent on the [`SyncSender`] will become available on the [`Receiver`]
 /// in the same order as it was sent. Like asynchronous [`channel`]s, the
 /// [`Receiver`] will block until a message becomes available. `sync_channel`