//! The `join` macro.
use proc_macro_hack::proc_macro_hack;
macro_rules! document_join_macro {
($join:item $try_join:item) => {
/// Polls multiple futures simultaneously, returning a tuple
/// of all results once complete.
///
/// While `join!(a, b)` is similar to `(a.await, b.await)`,
/// `join!` polls both futures concurrently and therefore is more efficent.
///
/// This macro is only usable inside of async functions, closures, and blocks.
/// It is also gated behind the `async-await` feature of this library, which is
/// activated by default.
///
/// # Examples
///
/// ```
/// # futures::executor::block_on(async {
/// use futures::join;
///
/// let a = async { 1 };
/// let b = async { 2 };
///
/// assert_eq!(join!(a, b), (1, 2));
/// # });
/// ```
$join
/// Polls multiple futures simultaneously, resolving to a [`Result`] containing
/// either a tuple of the successful outputs or an error.
///
/// `try_join!` is similar to [`join!`], but completes immediately if any of
/// the futures return an error.
///
/// This macro is only usable inside of async functions, closures, and blocks.
/// It is also gated behind the `async-await` feature of this library, which is
/// activated by default.
///
/// # Examples
///
/// When used on multiple futures that return `Ok`, `try_join!` will return
/// `Ok` of a tuple of the values:
///
/// ```
/// # futures::executor::block_on(async {
/// use futures::try_join;
///
/// let a = async { Ok::<i32, i32>(1) };
/// let b = async { Ok::<u64, i32>(2) };
///
/// assert_eq!(try_join!(a, b), Ok((1, 2)));
/// # });
/// ```
///
/// If one of the futures resolves to an error, `try_join!` will return
/// that error:
///
/// ```
/// # futures::executor::block_on(async {
/// use futures::try_join;
///
/// let a = async { Ok::<i32, i32>(1) };
/// let b = async { Err::<u64, i32>(2) };
///
/// assert_eq!(try_join!(a, b), Err(2));
/// # });
/// ```
$try_join
}
}
#[doc(hidden)]
#[proc_macro_hack(support_nested)]
pub use futures_macro::join_internal;
#[doc(hidden)]
#[proc_macro_hack(support_nested)]
pub use futures_macro::try_join_internal;
document_join_macro! {
#[macro_export]
macro_rules! join {
($($tokens:tt)*) => {{
use $crate::__reexport as __futures_crate;
$crate::join_internal! {
$( $tokens )*
}
}}
}
#[macro_export]
macro_rules! try_join {
($($tokens:tt)*) => {{
use $crate::__reexport as __futures_crate;
$crate::try_join_internal! {
$( $tokens )*
}
}}
}
}