Shorten even more panic temporary lifetimes

library/core/src/panic.rs

@@ -28,13 +28,13 @@ pub macro panic_2015 {
         $crate::panicking::panic($msg)
     ),
     // Use `panic_str` instead of `panic_display::<&str>` for non_fmt_panic lint.
-    ($msg:expr $(,)?) => (
-        $crate::panicking::panic_str($msg)
-    ),
+    ($msg:expr $(,)?) => ({
+        $crate::panicking::panic_str($msg);
+    }),
     // Special-case the single-argument case for const_panic.
-    ("{}", $arg:expr $(,)?) => (
-        $crate::panicking::panic_display(&$arg)
-    ),
+    ("{}", $arg:expr $(,)?) => ({
+        $crate::panicking::panic_display(&$arg);
+    }),
     ($fmt:expr, $($arg:tt)+) => ({
         // Semicolon to prevent temporaries inside the formatting machinery from
         // being considered alive in the caller after the panic_fmt call.
@@ -52,9 +52,9 @@ pub macro panic_2021 {
         $crate::panicking::panic("explicit panic")
     ),
     // Special-case the single-argument case for const_panic.
-    ("{}", $arg:expr $(,)?) => (
-        $crate::panicking::panic_display(&$arg)
-    ),
+    ("{}", $arg:expr $(,)?) => ({
+        $crate::panicking::panic_display(&$arg);
+    }),
     ($($t:tt)+) => ({
         // Semicolon to prevent temporaries inside the formatting machinery from
         // being considered alive in the caller after the panic_fmt call.
@@ -73,9 +73,9 @@ pub macro unreachable_2015 {
     ),
     // Use of `unreachable_display` for non_fmt_panic lint.
     // NOTE: the message ("internal error ...") is embedded directly in unreachable_display
-    ($msg:expr $(,)?) => (
-        $crate::panicking::unreachable_display(&$msg)
-    ),
+    ($msg:expr $(,)?) => ({
+        $crate::panicking::unreachable_display(&$msg);
+    }),
     ($fmt:expr, $($arg:tt)*) => (
         $crate::panic!($crate::concat!("internal error: entered unreachable code: ", $fmt), $($arg)*)
     ),

library/std/src/panic.rs

@@ -19,11 +19,11 @@ pub macro panic_2015 {
         $crate::rt::begin_panic("explicit panic")
     }),
     ($msg:expr $(,)?) => ({
-        $crate::rt::begin_panic($msg)
+        $crate::rt::begin_panic($msg);
     }),
     // Special-case the single-argument case for const_panic.
     ("{}", $arg:expr $(,)?) => ({
-        $crate::rt::panic_display(&$arg)
+        $crate::rt::panic_display(&$arg);
     }),
     ($fmt:expr, $($arg:tt)+) => ({
         // Semicolon to prevent temporaries inside the formatting machinery from

tests/ui/macros/panic-temporaries-2018.rs

@@ -0,0 +1,55 @@
+// check-pass
+// edition:2018
+
+#![allow(non_fmt_panics, unreachable_code)]
+
+use std::fmt::{self, Display};
+use std::marker::PhantomData;
+
+struct NotSend {
+    marker: PhantomData<*const u8>,
+}
+
+const NOT_SEND: NotSend = NotSend { marker: PhantomData };
+
+impl Display for NotSend {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("this value does not implement Send")
+    }
+}
+
+async fn f(_: u8) {}
+
+// Exercises this matcher in panic_2015:
+// ($fmt:expr, $($arg:tt)+) => $crate::panicking::panic_fmt(...)
+async fn panic_fmt() {
+    // Panic returns `!`, so the await is never reached, and in particular the
+    // temporaries inside the formatting machinery are not still alive at the
+    // await point.
+    let todo = "...";
+    f(panic!("not yet implemented: {}", todo)).await;
+}
+
+// Exercises ("{}", $arg:expr) => $crate::panicking::panic_display(&$arg)
+async fn panic_display() {
+    f(panic!("{}", NOT_SEND)).await;
+}
+
+// Exercises ($msg:expr) => $crate::panicking::panic_str($msg)
+async fn panic_str() {
+    f(panic!((NOT_SEND, "...").1)).await;
+}
+
+// Exercises ($msg:expr) => $crate::panicking::unreachable_display(&$msg)
+async fn unreachable_display() {
+    f(unreachable!(NOT_SEND)).await;
+}
+
+fn require_send(_: impl Send) {}
+
+fn main() {
+    require_send(panic_fmt());
+    require_send(panic_display());
+    require_send(panic_str());
+    require_send(unreachable_display());
+}

tests/ui/macros/panic-temporaries.rs

@@ -3,17 +3,41 @@
 
 #![allow(unreachable_code)]
 
+use std::fmt::{self, Display};
+use std::marker::PhantomData;
+
+struct NotSend {
+    marker: PhantomData<*const u8>,
+}
+
+const NOT_SEND: NotSend = NotSend { marker: PhantomData };
+
+impl Display for NotSend {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("this value does not implement Send")
+    }
+}
+
 async fn f(_: u8) {}
 
-async fn g() {
-    // Todo returns `!`, so the await is never reached, and in particular the
+// Exercises this matcher in panic_2021:
+// ($($t:tt)+) => $crate::panicking::panic_fmt(...)
+async fn panic_fmt() {
+    // Panic returns `!`, so the await is never reached, and in particular the
     // temporaries inside the formatting machinery are not still alive at the
     // await point.
-    f(todo!("...")).await;
+    let todo = "...";
+    f(panic!("not yet implemented: {}", todo)).await;
+}
+
+// Exercises ("{}", $arg:expr) => $crate::panicking::panic_display(&$arg)
+async fn panic_display() {
+    f(panic!("{}", NOT_SEND)).await;
 }
 
 fn require_send(_: impl Send) {}
 
 fn main() {
-    require_send(g());
+    require_send(panic_fmt());
+    require_send(panic_display());
 }