Rollup merge of #89508 - jhpratt:stabilize-const_panic, r=joshtriplett

Stabilize `const_panic`

Closes #51999

FCP completed in #89006

```@rustbot``` label +A-const-eval +A-const-fn +T-lang

cc ```@oli-obk``` for review (not `r?`'ing as not on lang team)

Author: workingjubilee

compiler/rustc_borrowck/src/lib.rs

@@ -2,7 +2,7 @@
 
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
-#![feature(const_panic)]
+#![cfg_attr(bootstrap, feature(const_panic))]
 #![feature(crate_visibility_modifier)]
 #![feature(format_args_capture)]
 #![feature(in_band_lifetimes)]

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -887,8 +887,6 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
 
                 // At this point, we are calling a function, `callee`, whose `DefId` is known...
                 if is_lang_panic_fn(tcx, callee) {
-                    self.check_op(ops::Panic);
-
                     // `begin_panic` and `panic_display` are generic functions that accept
                     // types other than str. Check to enforce that only str can be used in
                     // const-eval.

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -368,23 +368,6 @@ impl NonConstOp for MutDeref {
     }
 }
 
-#[derive(Debug)]
-pub struct Panic;
-impl NonConstOp for Panic {
-    fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status {
-        Status::Unstable(sym::const_panic)
-    }
-
-    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
-        feature_err(
-            &ccx.tcx.sess.parse_sess,
-            sym::const_panic,
-            span,
-            &format!("panicking in {}s is unstable", ccx.const_kind()),
-        )
-    }
-}
-
 /// A call to a `panic()` lang item where the first argument is _not_ a `&str`.
 #[derive(Debug)]
 pub struct PanicNonStr;

compiler/rustc_data_structures/src/lib.rs

@@ -11,7 +11,7 @@
 #![feature(associated_type_bounds)]
 #![feature(auto_traits)]
 #![feature(bool_to_option)]
-#![feature(const_panic)]
+#![cfg_attr(bootstrap, feature(const_panic))]
 #![feature(control_flow_enum)]
 #![feature(core_intrinsics)]
 #![feature(extend_one)]

compiler/rustc_feature/src/accepted.rs

@@ -297,6 +297,8 @@ declare_features! (
     (accepted, arbitrary_enum_discriminant, "1.56.0", Some(60553), None),
     /// Allows macro attributes to observe output of `#[derive]`.
     (accepted, macro_attributes_in_derive_output, "1.57.0", Some(81119), None),
+    /// Allows panicking during const eval (producing compile-time errors).
+    (accepted, const_panic, "1.57.0", Some(51999), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: accepted features

compiler/rustc_feature/src/active.rs

@@ -425,9 +425,6 @@ declare_features! (
     /// Allows using the `amdgpu-kernel` ABI.
     (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
 
-    /// Allows panicking during const eval (producing compile-time errors).
-    (active, const_panic, "1.30.0", Some(51999), None),
-
     /// Allows `#[marker]` on certain traits allowing overlapping implementations.
     (active, marker_trait_attr, "1.30.0", Some(29864), None),
 

compiler/rustc_index/src/vec.rs

@@ -124,7 +124,9 @@ macro_rules! newtype_index {
 
             #[inline]
             $v const fn from_usize(value: usize) -> Self {
-                // FIXME: replace with `assert!(value <= ($max as usize));` once `const_panic` is stable
+                #[cfg(not(bootstrap))]
+                assert!(value <= ($max as usize));
+                #[cfg(bootstrap)]
                 [()][(value > ($max as usize)) as usize];
                 unsafe {
                     Self::from_u32_unchecked(value as u32)
@@ -133,7 +135,9 @@ macro_rules! newtype_index {
 
             #[inline]
             $v const fn from_u32(value: u32) -> Self {
-                // FIXME: replace with `assert!(value <= $max);` once `const_panic` is stable
+                #[cfg(not(bootstrap))]
+                assert!(value <= $max);
+                #[cfg(bootstrap)]
                 [()][(value > $max) as usize];
                 unsafe {
                     Self::from_u32_unchecked(value)

compiler/rustc_mir_dataflow/src/lib.rs

@@ -2,7 +2,7 @@
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
-#![feature(const_panic)]
+#![cfg_attr(bootstrap, feature(const_panic))]
 #![feature(exact_size_is_empty)]
 #![feature(in_band_lifetimes)]
 #![feature(iter_zip)]

compiler/rustc_mir_transform/src/lib.rs

@@ -1,7 +1,7 @@
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
-#![feature(const_panic)]
+#![cfg_attr(bootstrap, feature(const_panic))]
 #![feature(in_band_lifetimes)]
 #![feature(iter_zip)]
 #![feature(map_try_insert)]

library/core/src/lib.rs

@@ -124,7 +124,7 @@
 #![feature(const_fn_trait_bound)]
 #![feature(const_impl_trait)]
 #![feature(const_mut_refs)]
-#![feature(const_panic)]
+#![cfg_attr(bootstrap, feature(const_panic))]
 #![feature(const_precise_live_drops)]
 #![feature(const_raw_ptr_deref)]
 #![feature(const_refs_to_cell)]