Add new const_format_args!() macro and use it in panics.

2 files changed, 6 insertions, 5 deletions

diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index f0e628c3d83..808a2202b3e 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -247,6 +247,7 @@
 #![feature(const_fn_floating_point_arithmetic)]
 #![feature(const_fn_fn_ptr_basics)]
 #![cfg_attr(bootstrap, feature(const_fn_transmute))]
+#![feature(const_format_args)]
 #![feature(const_io_structs)]
 #![feature(const_ip)]
 #![feature(const_ipv4)]
@@ -556,9 +557,9 @@ pub use core::{
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[allow(deprecated)]
 pub use core::{
-    assert, assert_matches, cfg, column, compile_error, concat, concat_idents, env, file,
-    format_args, format_args_nl, include, include_bytes, include_str, line, llvm_asm, log_syntax,
-    module_path, option_env, stringify, trace_macros,
+    assert, assert_matches, cfg, column, compile_error, concat, concat_idents, const_format_args,
+    env, file, format_args, format_args_nl, include, include_bytes, include_str, line, llvm_asm,
+    log_syntax, module_path, option_env, stringify, trace_macros,
 };
 
 #[stable(feature = "core_primitive", since = "1.43.0")]
diff --git a/library/std/src/panic.rs b/library/std/src/panic.rs
index 7bc987db881..3b3996e437c 100644
--- a/library/std/src/panic.rs
+++ b/library/std/src/panic.rs
@@ -20,7 +20,7 @@ use crate::thread::Result;
 
 #[doc(hidden)]
 #[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
-#[allow_internal_unstable(libstd_sys_internals)]
+#[allow_internal_unstable(libstd_sys_internals, const_format_args)]
 #[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_2015_macro")]
 #[rustc_macro_transparency = "semitransparent"]
 pub macro panic_2015 {
@@ -31,7 +31,7 @@ pub macro panic_2015 {
         $crate::rt::begin_panic($msg)
     }),
     ($fmt:expr, $($arg:tt)+) => ({
-        $crate::rt::begin_panic_fmt(&$crate::format_args!($fmt, $($arg)+))
+        $crate::rt::begin_panic_fmt(&$crate::const_format_args!($fmt, $($arg)+))
     }),
 }