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DarksonnDarksonn
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macros: allow temporary lifetime extension in select (#6722)
1 parent ee8d4d1 commit 438def7

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2 files changed

+218
-1
lines changed

2 files changed

+218
-1
lines changed

‎tokio/src/macros/select.rs

+210-1
Original file line numberDiff line numberDiff line change
@@ -489,13 +489,22 @@ doc! {macro_rules! select {
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// Create a scope to separate polling from handling the output. This
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// adds borrow checker flexibility when using the macro.
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let mut output = {
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// Store each future directly first (that is, without wrapping the future in a call to
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// `IntoFuture::into_future`). This allows the `$fut` expression to make use of
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// temporary lifetime extension.
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//
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// https://doc.rust-lang.org/1.58.1/reference/destructors.html#temporary-lifetime-extension
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let futures_init = ($( $fut, )+);
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// Safety: Nothing must be moved out of `futures`. This is to
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// satisfy the requirement of `Pin::new_unchecked` called below.
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//
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// We can't use the `pin!` macro for this because `futures` is a
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// tuple and the standard library provides no way to pin-project to
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// the fields of a tuple.
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let mut futures = ( $( $crate::macros::support::IntoFuture::into_future($fut) , )+ );
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let mut futures = ($( $crate::macros::support::IntoFuture::into_future(
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$crate::count_field!( futures_init.$($skip)* )
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),)+);
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// This assignment makes sure that the `poll_fn` closure only has a
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// reference to the futures, instead of taking ownership of them.
@@ -854,6 +863,206 @@ macro_rules! count {
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};
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}
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#[macro_export]
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#[doc(hidden)]
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macro_rules! count_field {
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($var:ident. ) => {
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$var.0
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};
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($var:ident. _) => {
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$var.1
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};
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($var:ident. _ _) => {
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$var.2
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};
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($var:ident. _ _ _) => {
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$var.3
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};
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($var:ident. _ _ _ _) => {
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$var.4
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};
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($var:ident. _ _ _ _ _) => {
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$var.5
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};
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($var:ident. _ _ _ _ _ _) => {
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$var.6
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};
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($var:ident. _ _ _ _ _ _ _) => {
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$var.7
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};
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($var:ident. _ _ _ _ _ _ _ _) => {
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$var.8
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};
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($var:ident. _ _ _ _ _ _ _ _ _) => {
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$var.9
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _) => {
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$var.10
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _) => {
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$var.11
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.12
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.13
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.14
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.15
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.16
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.17
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.18
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.19
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.20
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.21
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.22
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.23
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.24
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.25
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.26
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.27
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.28
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.29
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.30
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.31
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.32
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.33
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.34
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.35
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.36
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.37
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.38
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.39
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.40
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.41
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.42
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.43
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.44
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.45
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.46
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.47
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.48
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.49
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.50
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.51
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.52
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.53
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.54
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.55
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.56
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.57
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.58
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.59
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.60
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.61
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.62
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.63
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};
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($var:ident. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _) => {
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$var.64
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};
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}
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#[macro_export]
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#[doc(hidden)]
8591068
macro_rules! select_variant {

‎tokio/tests/macros_select.rs

+8
Original file line numberDiff line numberDiff line change
@@ -709,3 +709,11 @@ async fn select_into_future() {
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() = NotAFuture => {},
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}
711711
}
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// regression test for https://github.com/tokio-rs/tokio/issues/6721
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#[tokio::test]
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async fn temporary_lifetime_extension() {
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tokio::select! {
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() = &mut std::future::ready(()) => {},
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}
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}

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