From 425404fe59bf047cd7400fb7c1fd7942f2bd040a Mon Sep 17 00:00:00 2001
From: Hanna Kruppe <hanna.kruppe@gmail.com>
Date: Sun, 4 Oct 2026 20:47:09 +0200
Subject: [PATCH] outline some panics with constant messages

---
 library/core/src/macros/mod.rs |  2 +-
 library/core/src/panic.rs      | 35 ++++++++++++++++++++++++++++++----
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index ab8fc47009186..3d5a15ab6d582 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -802,7 +802,7 @@ macro_rules! unreachable {
 #[rustc_diagnostic_opaque]
 macro_rules! unimplemented {
     () => {
-        $crate::panicking::panic("not implemented")
+        $crate::panic::unimplemented_noargs()
     };
     ($($arg:tt)+) => {
         $crate::panic!("not implemented: {}", $crate::format_args!($($arg)+))
diff --git a/library/core/src/panic.rs b/library/core/src/panic.rs
index 4fcd5f615e993..0d3d7ef7e7130 100644
--- a/library/core/src/panic.rs
+++ b/library/core/src/panic.rs
@@ -22,7 +22,7 @@ pub use self::unwind_safe::{AssertUnwindSafe, RefUnwindSafe, UnwindSafe};
 #[rustc_macro_transparency = "semiopaque"]
 pub macro panic_2015 {
     () => (
-        $crate::panicking::panic("explicit panic")
+        $crate::panic::panic_noargs()
     ),
     ($msg:literal $(,)?) => (
         $crate::panicking::panic($msg)
@@ -49,7 +49,7 @@ pub macro panic_2015 {
 #[rustc_macro_transparency = "semiopaque"]
 pub macro panic_2021 {
     () => (
-        $crate::panicking::panic("explicit panic")
+        $crate::panic::panic_noargs()
     ),
     // Special-case the single-argument case for const_panic.
     ("{}", $arg:expr $(,)?) => ({
@@ -62,6 +62,15 @@ pub macro panic_2021 {
     }),
 }
 
+#[doc(hidden)]
+#[unstable(feature = "panic_internals", issue = "none")]
+#[cold]
+#[inline(never)]
+#[track_caller]
+pub const fn panic_noargs() -> ! {
+    crate::panicking::panic("explicit panic")
+}
+
 #[doc(hidden)]
 #[unstable(feature = "edition_panic", issue = "none", reason = "use unreachable!() instead")]
 #[allow_internal_unstable(panic_internals)]
@@ -69,7 +78,7 @@ pub macro panic_2021 {
 #[rustc_macro_transparency = "semiopaque"]
 pub macro unreachable_2015 {
     () => (
-        $crate::panicking::panic("internal error: entered unreachable code")
+        $crate::panic::unreachable_noargs()
     ),
     // Use of `unreachable_display` for non_fmt_panic lint.
     // NOTE: the message ("internal error ...") is embedded directly in unreachable_display
@@ -87,13 +96,31 @@ pub macro unreachable_2015 {
 #[rustc_macro_transparency = "semiopaque"]
 pub macro unreachable_2021 {
     () => (
-        $crate::panicking::panic("internal error: entered unreachable code")
+        $crate::panic::unreachable_noargs()
     ),
     ($($t:tt)+) => (
         $crate::panic!("internal error: entered unreachable code: {}", $crate::format_args!($($t)+))
     ),
 }
 
+#[doc(hidden)]
+#[unstable(feature = "panic_internals", issue = "none")]
+#[cold]
+#[inline(never)]
+#[track_caller]
+pub const fn unreachable_noargs() -> ! {
+    crate::panicking::panic("internal error: entered unreachable code")
+}
+
+#[doc(hidden)]
+#[unstable(feature = "panic_internals", issue = "none")]
+#[cold]
+#[inline(never)]
+#[track_caller]
+pub const fn unimplemented_noargs() -> ! {
+    crate::panicking::panic("not implemented")
+}
+
 /// Invokes a closure, aborting if the closure unwinds.
 ///
 /// When compiled with aborting panics, this function is effectively a no-op.