Revert "Partially outline code inside the panic! macro".

Without any tests/benchmarks that show some improvement, it's hard to
know whether the change had any positive effect at all. (And if it did,
whether that effect is still achieved today.)

Author: m-ou-se

core/src/panic.rs

@@ -48,7 +48,6 @@ pub macro panic_2015 {
 #[allow_internal_unstable(panic_internals, const_format_args)]
 #[rustc_diagnostic_item = "core_panic_2021_macro"]
 #[rustc_macro_transparency = "semitransparent"]
-#[cfg(feature = "panic_immediate_abort")]
 pub macro panic_2021 {
     () => (
         $crate::panicking::panic("explicit panic")
@@ -64,50 +63,6 @@ pub macro panic_2021 {
     }),
 }
 
-#[doc(hidden)]
-#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
-#[allow_internal_unstable(
-    panic_internals,
-    core_intrinsics,
-    const_dispatch,
-    const_eval_select,
-    const_format_args,
-    rustc_attrs
-)]
-#[rustc_diagnostic_item = "core_panic_2021_macro"]
-#[rustc_macro_transparency = "semitransparent"]
-#[cfg(not(feature = "panic_immediate_abort"))]
-pub macro panic_2021 {
-    () => ({
-        // Create a function so that the argument for `track_caller`
-        // can be moved inside if possible.
-        #[cold]
-        #[track_caller]
-        #[inline(never)]
-        const fn panic_cold_explicit() -> ! {
-            $crate::panicking::panic_explicit()
-        }
-        panic_cold_explicit();
-    }),
-    // Special-case the single-argument case for const_panic.
-    ("{}", $arg:expr $(,)?) => ({
-        #[cold]
-        #[track_caller]
-        #[inline(never)]
-        #[rustc_const_panic_str] // enforce a &&str argument in const-check and hook this by const-eval
-        #[rustc_do_not_const_check] // hooked by const-eval
-        const fn panic_cold_display<T: $crate::fmt::Display>(arg: &T) -> ! {
-            $crate::panicking::panic_display(arg)
-        }
-        panic_cold_display(&$arg);
-    }),
-    ($($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)]
 #[unstable(feature = "edition_panic", issue = "none", reason = "use unreachable!() instead")]
 #[allow_internal_unstable(panic_internals)]

core/src/panicking.rs

@@ -233,14 +233,6 @@ pub fn panic_nounwind_nobacktrace(expr: &'static str) -> ! {
     panic_nounwind_fmt(fmt::Arguments::new_const(&[expr]), /* force_no_backtrace */ true);
 }
 
-#[track_caller]
-#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
-#[cfg_attr(feature = "panic_immediate_abort", inline)]
-#[rustc_const_stable_indirect] // must follow stable const rules since it is exposed to stable
-pub const fn panic_explicit() -> ! {
-    panic_display(&"explicit panic");
-}
-
 #[inline]
 #[track_caller]
 #[rustc_diagnostic_item = "unreachable_display"] // needed for `non-fmt-panics` lint
@@ -260,9 +252,8 @@ pub const fn panic_str_2015(expr: &str) -> ! {
 
 #[inline]
 #[track_caller]
+#[lang = "panic_display"] // needed for const-evaluated panics
 #[rustc_do_not_const_check] // hooked by const-eval
-// enforce a &&str argument in const-check and hook this by const-eval
-#[rustc_const_panic_str]
 #[rustc_const_stable_indirect] // must follow stable const rules since it is exposed to stable
 pub const fn panic_display<T: fmt::Display>(x: &T) -> ! {
     panic_fmt(format_args!("{}", *x));