diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index bd62bc5c3056c..3a115a8b8b6c6 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -496,10 +496,9 @@ macro_rules! r#try {
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(test), rustc_diagnostic_item = "write_macro")]
macro_rules! write {
- ($dst:expr, $($arg:tt)*) => {{
- let result = $dst.write_fmt($crate::format_args!($($arg)*));
- result
- }};
+ ($dst:expr, $($arg:tt)*) => {
+ $dst.write_fmt($crate::format_args!($($arg)*))
+ };
}
/// Write formatted data into a buffer, with a newline appended.
@@ -554,10 +553,9 @@ macro_rules! writeln {
($dst:expr $(,)?) => {
$crate::write!($dst, "\n")
};
- ($dst:expr, $($arg:tt)*) => {{
- let result = $dst.write_fmt($crate::format_args_nl!($($arg)*));
- result
- }};
+ ($dst:expr, $($arg:tt)*) => {
+ $dst.write_fmt($crate::format_args_nl!($($arg)*))
+ };
}
/// Indicates unreachable code.
diff --git a/src/test/ui/macros/format-args-temporaries-async.rs b/src/test/ui/macros/format-args-temporaries-async.rs
new file mode 100644
index 0000000000000..d959329b9fce2
--- /dev/null
+++ b/src/test/ui/macros/format-args-temporaries-async.rs
@@ -0,0 +1,37 @@
+// check-pass
+// edition:2021
+
+use std::fmt::{self, Display};
+use std::future::Future;
+use std::io;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+struct AsyncStdout;
+
+impl AsyncStdout {
+ fn write_fmt<'a>(&'a mut self, _args: fmt::Arguments) -> WriteFmtFuture<'a, Self>
+ where
+ Self: Unpin,
+ {
+ WriteFmtFuture(self)
+ }
+}
+
+struct WriteFmtFuture<'a, T>(&'a mut T);
+
+impl<'a, T> Future for WriteFmtFuture<'a, T> {
+ type Output = io::Result<()>;
+ fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
+ unimplemented!()
+ }
+}
+
+async fn async_main() {
+ let _write = write!(&mut AsyncStdout, "...").await;
+ let _writeln = writeln!(&mut AsyncStdout, "...").await;
+}
+
+fn main() {
+ let _ = async_main;
+}
diff --git a/src/test/ui/macros/format-args-temporaries-in-write.rs b/src/test/ui/macros/format-args-temporaries-in-write.rs
new file mode 100644
index 0000000000000..339ccbc33ac98
--- /dev/null
+++ b/src/test/ui/macros/format-args-temporaries-in-write.rs
@@ -0,0 +1,50 @@
+// check-fail
+
+use std::fmt::{self, Display};
+
+struct Mutex;
+
+impl Mutex {
+ fn lock(&self) -> MutexGuard {
+ MutexGuard(self)
+ }
+}
+
+struct MutexGuard<'a>(&'a Mutex);
+
+impl<'a> Drop for MutexGuard<'a> {
+ fn drop(&mut self) {
+ // Empty but this is a necessary part of the repro. Otherwise borrow
+ // checker is fine with 'a dangling at the time that MutexGuard goes out
+ // of scope.
+ }
+}
+
+struct Out;
+
+impl Out {
+ fn write_fmt(&self, _args: fmt::Arguments) {}
+}
+
+impl<'a> Display for MutexGuard<'a> {
+ fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+ Ok(())
+ }
+}
+
+fn main() {
+ // FIXME(dtolnay): We actually want both of these to work. I think it's
+ // sadly unimplementable today though.
+
+ let _write = {
+ let mutex = Mutex;
+ write!(Out, "{}", mutex.lock()) /* no semicolon */
+ //~^ ERROR `mutex` does not live long enough
+ };
+
+ let _writeln = {
+ let mutex = Mutex;
+ writeln!(Out, "{}", mutex.lock()) /* no semicolon */
+ //~^ ERROR `mutex` does not live long enough
+ };
+}
diff --git a/src/test/ui/macros/format-args-temporaries-in-write.stderr b/src/test/ui/macros/format-args-temporaries-in-write.stderr
new file mode 100644
index 0000000000000..03ecc4b4418c6
--- /dev/null
+++ b/src/test/ui/macros/format-args-temporaries-in-write.stderr
@@ -0,0 +1,43 @@
+error[E0597]: `mutex` does not live long enough
+ --> $DIR/format-args-temporaries-in-write.rs:41:27
+ |
+LL | write!(Out, "{}", mutex.lock()) /* no semicolon */
+ | ^^^^^^^^^^^^
+ | |
+ | borrowed value does not live long enough
+ | a temporary with access to the borrow is created here ...
+LL |
+LL | };
+ | -- ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `MutexGuard`
+ | |
+ | `mutex` dropped here while still borrowed
+ |
+help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
+ --> $SRC_DIR/core/src/macros/mod.rs:LL:COL
+ |
+LL | $dst.write_fmt($crate::format_args!($($arg)*));
+ | +
+
+error[E0597]: `mutex` does not live long enough
+ --> $DIR/format-args-temporaries-in-write.rs:47:29
+ |
+LL | writeln!(Out, "{}", mutex.lock()) /* no semicolon */
+ | ^^^^^^^^^^^^
+ | |
+ | borrowed value does not live long enough
+ | a temporary with access to the borrow is created here ...
+LL |
+LL | };
+ | -- ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `MutexGuard`
+ | |
+ | `mutex` dropped here while still borrowed
+ |
+help: consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped
+ --> $SRC_DIR/core/src/macros/mod.rs:LL:COL
+ |
+LL | $dst.write_fmt($crate::format_args_nl!($($arg)*));
+ | +
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0597`.
diff --git a/src/test/ui/macros/format-args-temporaries.rs b/src/test/ui/macros/format-args-temporaries.rs
index ddd4c9754bfa4..59323828bc37f 100644
--- a/src/test/ui/macros/format-args-temporaries.rs
+++ b/src/test/ui/macros/format-args-temporaries.rs
@@ -20,10 +20,6 @@ impl<'a> Drop for MutexGuard<'a> {
}
}
-impl<'a> MutexGuard<'a> {
- fn write_fmt(&self, _args: fmt::Arguments) {}
-}
-
impl<'a> Display for MutexGuard<'a> {
fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
Ok(())
@@ -31,18 +27,6 @@ impl<'a> Display for MutexGuard<'a> {
}
fn main() {
- let _write = {
- let out = Mutex;
- let mutex = Mutex;
- write!(out.lock(), "{}", mutex.lock()) /* no semicolon */
- };
-
- let _writeln = {
- let out = Mutex;
- let mutex = Mutex;
- writeln!(out.lock(), "{}", mutex.lock()) /* no semicolon */
- };
-
let _print = {
let mutex = Mutex;
print!("{}", mutex.lock()) /* no semicolon */