Fix const core::panic!(non_literal_str).

Author: m-ou-se

compiler/rustc_hir/src/lang_items.rs

@@ -263,6 +263,7 @@ language_item_table! {
     // is required to define it somewhere. Additionally, there are restrictions on crates that use
     // a weak lang item, but do not have it defined.
     Panic,                   sym::panic,               panic_fn,                   Target::Fn;
+    PanicStr,                sym::panic_str,           panic_str,                  Target::Fn;
     PanicBoundsCheck,        sym::panic_bounds_check,  panic_bounds_check_fn,      Target::Fn;
     PanicInfo,               sym::panic_info,          panic_info,                 Target::Struct;
     PanicLocation,           sym::panic_location,      panic_location,             Target::Struct;

compiler/rustc_mir/src/const_eval/machine.rs

@@ -70,9 +70,10 @@ impl<'mir, 'tcx> InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>> {
     ) -> InterpResult<'tcx> {
         let def_id = instance.def_id();
         if Some(def_id) == self.tcx.lang_items().panic_fn()
+            || Some(def_id) == self.tcx.lang_items().panic_str()
             || Some(def_id) == self.tcx.lang_items().begin_panic_fn()
         {
-            // &'static str
+            // &str
             assert!(args.len() == 1);
 
             let msg_place = self.deref_operand(args[0])?;

compiler/rustc_mir/src/transform/check_consts/mod.rs

@@ -74,7 +74,9 @@ impl ConstCx<'mir, 'tcx> {
 
 /// Returns `true` if this `DefId` points to one of the official `panic` lang items.
 pub fn is_lang_panic_fn(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
-    Some(def_id) == tcx.lang_items().panic_fn() || Some(def_id) == tcx.lang_items().begin_panic_fn()
+    Some(def_id) == tcx.lang_items().panic_fn()
+        || Some(def_id) == tcx.lang_items().panic_str()
+        || Some(def_id) == tcx.lang_items().begin_panic_fn()
 }
 
 pub fn allow_internal_unstable(tcx: TyCtxt<'tcx>, def_id: DefId, feature_gate: Symbol) -> bool {

compiler/rustc_span/src/symbol.rs

@@ -777,6 +777,7 @@ symbols! {
         panic_info,
         panic_location,
         panic_runtime,
+        panic_str,
         panic_unwind,
         param_attrs,
         parent_trait,

library/core/src/macros/mod.rs

@@ -10,7 +10,7 @@ macro_rules! panic {
         $crate::panicking::panic($msg)
     );
     ($msg:expr) => (
-        $crate::panic!("{}", $crate::convert::identity::<&str>($msg))
+        $crate::panicking::panic_str($msg)
     );
     ($msg:expr,) => (
         $crate::panic!($msg)

library/core/src/panicking.rs

@@ -50,6 +50,13 @@ pub fn panic(expr: &'static str) -> ! {
     panic_fmt(fmt::Arguments::new_v1(&[expr], &[]));
 }
 
+#[inline]
+#[track_caller]
+#[cfg_attr(not(bootstrap), lang = "panic_str")] // needed for const-evaluated panics
+pub fn panic_str(expr: &str) -> ! {
+    panic_fmt(format_args!("{}", expr));
+}
+
 #[cold]
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
 #[track_caller]