tokio: update code according to new MSRV (#6764)

tokio-util/src/codec/length_delimited.rs

@@ -1049,28 +1049,13 @@ impl Builder {
     }
 
     fn adjust_max_frame_len(&mut self) {
-        // This function is basically `std::u64::saturating_add_signed`. Since it
-        // requires MSRV 1.66, its implementation is copied here.
-        //
-        // TODO: use the method from std when MSRV becomes >= 1.66
-        fn saturating_add_signed(num: u64, rhs: i64) -> u64 {
-            let (res, overflow) = num.overflowing_add(rhs as u64);
-            if overflow == (rhs < 0) {
-                res
-            } else if overflow {
-                u64::MAX
-            } else {
-                0
-            }
-        }
-
         // Calculate the maximum number that can be represented using `length_field_len` bytes.
         let max_number = match 1u64.checked_shl((8 * self.length_field_len) as u32) {
             Some(shl) => shl - 1,
             None => u64::MAX,
         };
 
-        let max_allowed_len = saturating_add_signed(max_number, self.length_adjustment as i64);
+        let max_allowed_len = max_number.saturating_add_signed(self.length_adjustment as i64);
 
         if self.max_frame_len as u64 > max_allowed_len {
             self.max_frame_len = usize::try_from(max_allowed_len).unwrap_or(usize::MAX);

tokio/src/fs/try_exists.rs

@@ -24,11 +24,5 @@ use std::path::Path;
 /// ```
 pub async fn try_exists(path: impl AsRef<Path>) -> io::Result<bool> {
     let path = path.as_ref().to_owned();
-    // std's Path::try_exists is not available for current Rust min supported version.
+    asyncify(move || path.try_exists()).await
-    // Current implementation is based on its internal implementation instead.
-    match asyncify(move || std::fs::metadata(path)).await {
-        Ok(_) => Ok(true),
-        Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(false),
-        Err(error) => Err(error),
-    }
 }

tokio/src/io/util/read_int.rs

@@ -6,13 +6,12 @@ use std::future::Future;
 use std::io;
 use std::io::ErrorKind::UnexpectedEof;
 use std::marker::PhantomPinned;
-use std::mem::size_of;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
 macro_rules! reader {
     ($name:ident, $ty:ty, $reader:ident) => {
-        reader!($name, $ty, $reader, size_of::<$ty>());
+        reader!($name, $ty, $reader, std::mem::size_of::<$ty>());
     };
     ($name:ident, $ty:ty, $reader:ident, $bytes:expr) => {
         pin_project! {

tokio/src/io/util/write_int.rs

@@ -5,13 +5,12 @@ use pin_project_lite::pin_project;
 use std::future::Future;
 use std::io;
 use std::marker::PhantomPinned;
-use std::mem::size_of;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
 macro_rules! writer {
     ($name:ident, $ty:ty, $writer:ident) => {
-        writer!($name, $ty, $writer, size_of::<$ty>());
+        writer!($name, $ty, $writer, std::mem::size_of::<$ty>());
     };
     ($name:ident, $ty:ty, $writer:ident, $bytes:expr) => {
         pin_project! {

tokio/src/runtime/blocking/pool.rs

@@ -461,7 +461,7 @@ impl Spawner {
         shutdown_tx: shutdown::Sender,
         rt: &Handle,
         id: usize,
-    ) -> std::io::Result<thread::JoinHandle<()>> {
+    ) -> io::Result<thread::JoinHandle<()>> {
         let mut builder = thread::Builder::new().name((self.inner.thread_name)());
 
         if let Some(stack_size) = self.inner.stack_size {
@@ -497,8 +497,8 @@ cfg_unstable_metrics! {
 
 // Tells whether the error when spawning a thread is temporary.
 #[inline]
-fn is_temporary_os_thread_error(error: &std::io::Error) -> bool {
+fn is_temporary_os_thread_error(error: &io::Error) -> bool {
-    matches!(error.kind(), std::io::ErrorKind::WouldBlock)
+    matches!(error.kind(), io::ErrorKind::WouldBlock)
 }
 
 impl Inner {

tokio/src/runtime/scheduler/multi_thread/worker.rs

@@ -1014,7 +1014,7 @@ impl Core {
             .tuned_global_queue_interval(&worker.handle.shared.config);
 
         // Smooth out jitter
-        if abs_diff(self.global_queue_interval, next) > 2 {
+        if u32::abs_diff(self.global_queue_interval, next) > 2 {
             self.global_queue_interval = next;
         }
     }
@@ -1249,12 +1249,3 @@ fn with_current<R>(f: impl FnOnce(Option<&Context>) -> R) -> R {
         _ => f(None),
     })
 }
-
-// `u32::abs_diff` is not available on Tokio's MSRV.
-fn abs_diff(a: u32, b: u32) -> u32 {
-    if a > b {
-        a - b
-    } else {
-        b - a
-    }
-}

tokio/src/runtime/scheduler/multi_thread_alt/worker.rs

@@ -1292,7 +1292,7 @@ impl Worker {
         let next = core.stats.tuned_global_queue_interval(&cx.shared().config);
 
         // Smooth out jitter
-        if abs_diff(self.global_queue_interval, next) > 2 {
+        if u32::abs_diff(self.global_queue_interval, next) > 2 {
             self.global_queue_interval = next;
         }
     }
@@ -1592,12 +1592,3 @@ fn with_current<R>(f: impl FnOnce(Option<&Context>) -> R) -> R {
         _ => f(None),
     })
 }
-
-// `u32::abs_diff` is not available on Tokio's MSRV.
-fn abs_diff(a: u32, b: u32) -> u32 {
-    if a > b {
-        a - b
-    } else {
-        b - a
-    }
-}

tokio/src/runtime/task/core.rs

@@ -489,7 +489,5 @@ impl Trailer {
 #[test]
 #[cfg(not(loom))]
 fn header_lte_cache_line() {
-    use std::mem::size_of;
+    assert!(std::mem::size_of::<Header>() <= 8 * std::mem::size_of::<*const ()>());
-
-    assert!(size_of::<Header>() <= 8 * size_of::<*const ()>());
 }

tokio/src/task/spawn.rs

@@ -5,7 +5,7 @@ use std::future::Future;
 
 cfg_rt! {
     /// Spawns a new asynchronous task, returning a
-    /// [`JoinHandle`](super::JoinHandle) for it.
+    /// [`JoinHandle`](JoinHandle) for it.
     ///
     /// The provided future will start running in the background immediately
     /// when `spawn` is called, even if you don't await the returned

tokio/src/util/bit.rs

@@ -16,7 +16,7 @@ impl Pack {
 
     /// Value is packed in the `width` more-significant bits.
     pub(crate) const fn then(&self, width: u32) -> Pack {
-        let shift = pointer_width() - self.mask.leading_zeros();
+        let shift = usize::BITS - self.mask.leading_zeros();
         let mask = mask_for(width) << shift;
 
         Pack { mask, shift }
@@ -24,7 +24,7 @@ impl Pack {
 
     /// Width, in bits, dedicated to storing the value.
     pub(crate) const fn width(&self) -> u32 {
-        pointer_width() - (self.mask >> self.shift).leading_zeros()
+        usize::BITS - (self.mask >> self.shift).leading_zeros()
     }
 
     /// Max representable value.
@@ -52,11 +52,6 @@ impl fmt::Debug for Pack {
     }
 }
 
-/// Returns the width of a pointer in bits.
-pub(crate) const fn pointer_width() -> u32 {
-    std::mem::size_of::<usize>() as u32 * 8
-}
-
 /// Returns a `usize` with the right-most `n` bits set.
 pub(crate) const fn mask_for(n: u32) -> usize {
     let shift = 1usize.wrapping_shl(n - 1);

tokio/tests/io_async_fd.rs

@@ -372,7 +372,7 @@ async fn multiple_waiters() {
             panic!("Tasks exited unexpectedly")
         },
         _ = barrier.wait() => {}
-    };
+    }
 
     b.write_all(b"0").unwrap();