From cb109a672d161ee305d21c98edb84ef50c6f997b Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Mon, 7 Nov 2022 13:23:16 -0800
Subject: [PATCH] Shorten lifetime of panic temporaries in panic_fmt case

---
 library/core/src/panic.rs                     | 16 ++++++-----
 library/std/src/panic.rs                      |  4 ++-
 tests/ui/macros/panic-temporaries.rs          |  4 +--
 tests/ui/macros/panic-temporaries.stderr      | 27 -------------------
 ...ming-methods-have-optimized-codegen.stdout | 18 ++++++-------
 5 files changed, 24 insertions(+), 45 deletions(-)
 delete mode 100644 tests/ui/macros/panic-temporaries.stderr

diff --git a/library/core/src/panic.rs b/library/core/src/panic.rs
index 8338a5d7e5a..ebcce79b0f8 100644
--- a/library/core/src/panic.rs
+++ b/library/core/src/panic.rs
@@ -35,9 +35,11 @@ pub macro panic_2015 {
     ("{}", $arg:expr $(,)?) => (
         $crate::panicking::panic_display(&$arg)
     ),
-    ($fmt:expr, $($arg:tt)+) => (
-        $crate::panicking::panic_fmt($crate::const_format_args!($fmt, $($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.
+        $crate::panicking::panic_fmt($crate::const_format_args!($fmt, $($arg)+));
+    }),
 }
 
 #[doc(hidden)]
@@ -53,9 +55,11 @@ pub macro panic_2021 {
     ("{}", $arg:expr $(,)?) => (
         $crate::panicking::panic_display(&$arg)
     ),
-    ($($t:tt)+) => (
-        $crate::panicking::panic_fmt($crate::const_format_args!($($t)+))
-    ),
+    ($($t:tt)+) => ({
+        // Semicolon to prevent temporaries inside the formatting machinery from
+        // being considered alive in the caller after the panic_fmt call.
+        $crate::panicking::panic_fmt($crate::const_format_args!($($t)+));
+    }),
 }
 
 #[doc(hidden)]
diff --git a/library/std/src/panic.rs b/library/std/src/panic.rs
index 345d72ef867..a2ffd8b1e7e 100644
--- a/library/std/src/panic.rs
+++ b/library/std/src/panic.rs
@@ -26,7 +26,9 @@ pub macro panic_2015 {
         $crate::rt::panic_display(&$arg)
     }),
     ($fmt:expr, $($arg:tt)+) => ({
-        $crate::rt::panic_fmt($crate::const_format_args!($fmt, $($arg)+))
+        // Semicolon to prevent temporaries inside the formatting machinery from
+        // being considered alive in the caller after the panic_fmt call.
+        $crate::rt::panic_fmt($crate::const_format_args!($fmt, $($arg)+));
     }),
 }
 
diff --git a/tests/ui/macros/panic-temporaries.rs b/tests/ui/macros/panic-temporaries.rs
index 5ca139daf4e..5b5b8b7c2d9 100644
--- a/tests/ui/macros/panic-temporaries.rs
+++ b/tests/ui/macros/panic-temporaries.rs
@@ -1,4 +1,4 @@
-// check-fail
+// check-pass
 // edition:2021
 
 #![allow(unreachable_code)]
@@ -15,5 +15,5 @@ async fn g() {
 fn require_send(_: impl Send) {}
 
 fn main() {
-    require_send(g()); //~ future cannot be sent between threads safely
+    require_send(g());
 }
diff --git a/tests/ui/macros/panic-temporaries.stderr b/tests/ui/macros/panic-temporaries.stderr
deleted file mode 100644
index 425409dda69..00000000000
--- a/tests/ui/macros/panic-temporaries.stderr
+++ /dev/null
@@ -1,27 +0,0 @@
-error: future cannot be sent between threads safely
-  --> $DIR/panic-temporaries.rs:18:18
-   |
-LL |     require_send(g());
-   |                  ^^^ future returned by `g` is not `Send`
-   |
-   = help: the trait `Sync` is not implemented for `core::fmt::Opaque`
-note: future is not `Send` as this value is used across an await
-  --> $DIR/panic-temporaries.rs:12:20
-   |
-LL |     f(todo!("...")).await;
-   |       ------------ ^^^^^^ await occurs here, with `$crate::format_args!($($arg)+)` maybe used later
-   |       |
-   |       has type `ArgumentV1<'_>` which is not `Send`
-note: `$crate::format_args!($($arg)+)` is later dropped here
-  --> $DIR/panic-temporaries.rs:12:26
-   |
-LL |     f(todo!("...")).await;
-   |                          ^
-note: required by a bound in `require_send`
-  --> $DIR/panic-temporaries.rs:15:25
-   |
-LL | fn require_send(_: impl Send) {}
-   |                         ^^^^ required by this bound in `require_send`
-
-error: aborting due to previous error
-
diff --git a/tests/ui/macros/rfc-2011-nicer-assert-messages/non-consuming-methods-have-optimized-codegen.stdout b/tests/ui/macros/rfc-2011-nicer-assert-messages/non-consuming-methods-have-optimized-codegen.stdout
index ad97f7a4a75..b69b5bc3b53 100644
--- a/tests/ui/macros/rfc-2011-nicer-assert-messages/non-consuming-methods-have-optimized-codegen.stdout
+++ b/tests/ui/macros/rfc-2011-nicer-assert-messages/non-consuming-methods-have-optimized-codegen.stdout
@@ -26,7 +26,7 @@ fn arbitrary_consuming_method_for_demonstration_purposes() {
 
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: elem as usize\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };
@@ -42,7 +42,7 @@ fn addr_of() {
                 (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: &elem\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };
@@ -58,7 +58,7 @@ fn binary() {
                 (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: elem == 1\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };
@@ -71,7 +71,7 @@ fn binary() {
                 (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: elem >= 1\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };
@@ -84,7 +84,7 @@ fn binary() {
                 (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: elem > 0\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };
@@ -97,7 +97,7 @@ fn binary() {
                 (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: elem < 3\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };
@@ -110,7 +110,7 @@ fn binary() {
                 (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: elem <= 3\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };
@@ -123,7 +123,7 @@ fn binary() {
                 (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: elem != 3\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };
@@ -139,7 +139,7 @@ fn unary() {
                 (&::core::asserting::Wrapper(__local_bind0)).try_capture(&mut __capture0);
                 {
                     ::std::rt::panic_fmt(format_args!("Assertion failed: *elem\nWith captures:\n  elem = {0:?}\n",
-                            __capture0))
+                            __capture0));
                 }
             }
     };