diff --git a/compiler/rustc_codegen_cranelift/example/mini_core.rs b/compiler/rustc_codegen_cranelift/example/mini_core.rs
index 79820232496..72c9df59d83 100644
--- a/compiler/rustc_codegen_cranelift/example/mini_core.rs
+++ b/compiler/rustc_codegen_cranelift/example/mini_core.rs
@@ -620,70 +620,31 @@ pub union MaybeUninit<T> {
pub mod intrinsics {
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn abort() -> ! {
- loop {}
- }
+ pub fn abort() -> !;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn size_of<T>() -> usize {
- loop {}
- }
+ pub fn size_of<T>() -> usize;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn size_of_val<T: ?::Sized>(_val: *const T) -> usize {
- loop {}
- }
+ pub unsafe fn size_of_val<T: ?::Sized>(_val: *const T) -> usize;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn min_align_of<T>() -> usize {
- loop {}
- }
+ pub fn min_align_of<T>() -> usize;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn min_align_of_val<T: ?::Sized>(_val: *const T) -> usize {
- loop {}
- }
+ pub unsafe fn min_align_of_val<T: ?::Sized>(_val: *const T) -> usize;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn copy<T>(_src: *const T, _dst: *mut T, _count: usize) {
- loop {}
- }
+ pub unsafe fn copy<T>(_src: *const T, _dst: *mut T, _count: usize);
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn transmute<T, U>(_e: T) -> U {
- loop {}
- }
+ pub unsafe fn transmute<T, U>(_e: T) -> U;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn ctlz_nonzero<T>(_x: T) -> u32 {
- loop {}
- }
+ pub unsafe fn ctlz_nonzero<T>(_x: T) -> u32;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn needs_drop<T: ?::Sized>() -> bool {
- loop {}
- }
+ pub fn needs_drop<T: ?::Sized>() -> bool;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn bitreverse<T>(_x: T) -> T {
- loop {}
- }
+ pub fn bitreverse<T>(_x: T) -> T;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn bswap<T>(_x: T) -> T {
- loop {}
- }
+ pub fn bswap<T>(_x: T) -> T;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn write_bytes<T>(_dst: *mut T, _val: u8, _count: usize) {
- loop {}
- }
+ pub unsafe fn write_bytes<T>(_dst: *mut T, _val: u8, _count: usize);
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn unreachable() -> ! {
- loop {}
- }
+ pub unsafe fn unreachable() -> !;
}
pub mod libc {
diff --git a/compiler/rustc_codegen_gcc/example/mini_core.rs b/compiler/rustc_codegen_gcc/example/mini_core.rs
index 2ff1d757fd4..3dad35bc4ce 100644
--- a/compiler/rustc_codegen_gcc/example/mini_core.rs
+++ b/compiler/rustc_codegen_gcc/example/mini_core.rs
@@ -591,70 +591,31 @@ pub union MaybeUninit<T> {
pub mod intrinsics {
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn abort() -> ! {
- loop {}
- }
+ pub fn abort() -> !;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn size_of<T>() -> usize {
- loop {}
- }
+ pub fn size_of<T>() -> usize;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn size_of_val<T: ?::Sized>(_val: *const T) -> usize {
- loop {}
- }
+ pub unsafe fn size_of_val<T: ?::Sized>(_val: *const T) -> usize;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn min_align_of<T>() -> usize {
- loop {}
- }
+ pub fn min_align_of<T>() -> usize;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn min_align_of_val<T: ?::Sized>(_val: *const T) -> usize {
- loop {}
- }
+ pub unsafe fn min_align_of_val<T: ?::Sized>(_val: *const T) -> usize;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn copy<T>(_src: *const T, _dst: *mut T, _count: usize) {
- loop {}
- }
+ pub unsafe fn copy<T>(_src: *const T, _dst: *mut T, _count: usize);
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn transmute<T, U>(_e: T) -> U {
- loop {}
- }
+ pub unsafe fn transmute<T, U>(_e: T) -> U;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn ctlz_nonzero<T>(_x: T) -> u32 {
- loop {}
- }
+ pub unsafe fn ctlz_nonzero<T>(_x: T) -> u32;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn needs_drop<T: ?::Sized>() -> bool {
- loop {}
- }
+ pub fn needs_drop<T: ?::Sized>() -> bool;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn bitreverse<T>(_x: T) -> T {
- loop {}
- }
+ pub fn bitreverse<T>(_x: T) -> T;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn bswap<T>(_x: T) -> T {
- loop {}
- }
+ pub fn bswap<T>(_x: T) -> T;
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn write_bytes<T>(_dst: *mut T, _val: u8, _count: usize) {
- loop {}
- }
+ pub unsafe fn write_bytes<T>(_dst: *mut T, _val: u8, _count: usize);
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub unsafe fn unreachable() -> ! {
- loop {}
- }
+ pub unsafe fn unreachable() -> !;
}
pub mod libc {
diff --git a/compiler/rustc_codegen_gcc/tests/run/abort1.rs b/compiler/rustc_codegen_gcc/tests/run/abort1.rs
index 385e41a6881..fe46d9ae418 100644
--- a/compiler/rustc_codegen_gcc/tests/run/abort1.rs
+++ b/compiler/rustc_codegen_gcc/tests/run/abort1.rs
@@ -36,10 +36,7 @@ mod intrinsics {
#[rustc_nounwind]
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn abort() -> ! {
- loop {}
- }
+ pub fn abort() -> !;
}
/*
diff --git a/compiler/rustc_codegen_gcc/tests/run/abort2.rs b/compiler/rustc_codegen_gcc/tests/run/abort2.rs
index 6c66a930e07..4123f4f4bee 100644
--- a/compiler/rustc_codegen_gcc/tests/run/abort2.rs
+++ b/compiler/rustc_codegen_gcc/tests/run/abort2.rs
@@ -36,10 +36,7 @@ mod intrinsics {
#[rustc_nounwind]
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn abort() -> ! {
- loop {}
- }
+ pub fn abort() -> !;
}
/*
diff --git a/compiler/rustc_codegen_gcc/tests/run/assign.rs b/compiler/rustc_codegen_gcc/tests/run/assign.rs
index 4d414c577a6..286155852d5 100644
--- a/compiler/rustc_codegen_gcc/tests/run/assign.rs
+++ b/compiler/rustc_codegen_gcc/tests/run/assign.rs
@@ -59,10 +59,7 @@ mod libc {
mod intrinsics {
#[rustc_nounwind]
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn abort() -> ! {
- loop {}
- }
+ pub fn abort() -> !;
}
#[lang = "panic"]
diff --git a/compiler/rustc_codegen_gcc/tests/run/mut_ref.rs b/compiler/rustc_codegen_gcc/tests/run/mut_ref.rs
index 9be64f991ee..b0215860406 100644
--- a/compiler/rustc_codegen_gcc/tests/run/mut_ref.rs
+++ b/compiler/rustc_codegen_gcc/tests/run/mut_ref.rs
@@ -61,10 +61,7 @@ mod libc {
mod intrinsics {
#[rustc_nounwind]
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn abort() -> ! {
- loop {}
- }
+ pub fn abort() -> !;
}
#[lang = "panic"]
diff --git a/compiler/rustc_codegen_gcc/tests/run/operations.rs b/compiler/rustc_codegen_gcc/tests/run/operations.rs
index c92d3cc0b8f..8ba7a4c5ed8 100644
--- a/compiler/rustc_codegen_gcc/tests/run/operations.rs
+++ b/compiler/rustc_codegen_gcc/tests/run/operations.rs
@@ -67,10 +67,7 @@ mod libc {
mod intrinsics {
#[rustc_nounwind]
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn abort() -> ! {
- loop {}
- }
+ pub fn abort() -> !;
}
#[lang = "panic"]
diff --git a/compiler/rustc_codegen_gcc/tests/run/static.rs b/compiler/rustc_codegen_gcc/tests/run/static.rs
index 80c8782c4b1..c3c8121b1e1 100644
--- a/compiler/rustc_codegen_gcc/tests/run/static.rs
+++ b/compiler/rustc_codegen_gcc/tests/run/static.rs
@@ -49,10 +49,7 @@ mod intrinsics {
#[rustc_nounwind]
#[rustc_intrinsic]
- #[rustc_intrinsic_must_be_overridden]
- pub fn abort() -> ! {
- loop {}
- }
+ pub fn abort() -> !;
}
mod libc {
diff --git a/compiler/rustc_error_codes/src/error_codes/E0094.md b/compiler/rustc_error_codes/src/error_codes/E0094.md
index efbfa0851a8..909da368f2b 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0094.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0094.md
@@ -7,12 +7,8 @@ Erroneous code example:
#![allow(internal_features)]
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-fn size_of<T, U>() -> usize // error: intrinsic has wrong number
- // of type parameters
-{
- loop {}
-}
+fn size_of<T, U>() -> usize; // error: intrinsic has wrong number
+ // of type parameters
```
Please check that you provided the right number of type parameters
@@ -24,9 +20,5 @@ Example:
#![allow(internal_features)]
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-fn size_of<T>() -> usize // ok!
-{
- loop {}
-}
+fn size_of<T>() -> usize; // ok!
```
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index b2ada8fe61e..6d16dc00ef4 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -1005,10 +1005,6 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
rustc_intrinsic, Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes, intrinsics,
"the `#[rustc_intrinsic]` attribute is used to declare intrinsics as function items",
),
- gated!(
- rustc_intrinsic_must_be_overridden, Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes, intrinsics,
- "the `#[rustc_intrinsic_must_be_overridden]` attribute is used to declare intrinsics without real bodies",
- ),
rustc_attr!(
rustc_no_mir_inline, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes,
"#[rustc_no_mir_inline] prevents the MIR inliner from inlining a function while not affecting codegen"
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 88d57498542..c153f6bb7d7 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -1755,13 +1755,12 @@ pub fn intrinsic_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::Intrinsi
&& (matches!(tcx.fn_sig(def_id).skip_binder().abi(), ExternAbi::RustIntrinsic)
|| tcx.has_attr(def_id, sym::rustc_intrinsic))
{
- let must_be_overridden = tcx.has_attr(def_id, sym::rustc_intrinsic_must_be_overridden)
- || match tcx.hir_node_by_def_id(def_id) {
- hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn { has_body, .. }, .. }) => {
- !has_body
- }
- _ => true,
- };
+ let must_be_overridden = match tcx.hir_node_by_def_id(def_id) {
+ hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn { has_body, .. }, .. }) => {
+ !has_body
+ }
+ _ => true,
+ };
Some(ty::IntrinsicDef {
name: tcx.item_name(def_id.into()),
must_be_overridden,
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 10c79b1be82..e5457991e46 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1764,7 +1764,6 @@ symbols! {
rustc_insignificant_dtor,
rustc_intrinsic,
rustc_intrinsic_const_stable_indirect,
- rustc_intrinsic_must_be_overridden,
rustc_layout,
rustc_layout_scalar_valid_range_end,
rustc_layout_scalar_valid_range_start,
diff --git a/src/doc/unstable-book/src/language-features/intrinsics.md b/src/doc/unstable-book/src/language-features/intrinsics.md
index 13a6814d31b..975b400447e 100644
--- a/src/doc/unstable-book/src/language-features/intrinsics.md
+++ b/src/doc/unstable-book/src/language-features/intrinsics.md
@@ -62,13 +62,19 @@ These must be implemented by all backends.
### `#[rustc_intrinsic]` declarations
-These are written like intrinsics with fallback bodies, but the body is irrelevant.
-Use `loop {}` for the body or call the intrinsic recursively and add
-`#[rustc_intrinsic_must_be_overridden]` to the function to ensure that backends don't
-invoke the body.
+These are written without a body:
+```rust
+#![feature(intrinsics)]
+#![allow(internal_features)]
+
+#[rustc_intrinsic]
+pub fn abort() -> !;
+```
### Legacy extern ABI based intrinsics
+*This style is deprecated, always prefer the above form.*
+
These are imported as if they were FFI functions, with the special
`rust-intrinsic` ABI. For example, if one was in a freestanding
context, but wished to be able to `transmute` between types, and
diff --git a/tests/assembly/rust-abi-arg-attr.rs b/tests/assembly/rust-abi-arg-attr.rs
index e55a53fbdeb..5b5eeb29f0f 100644
--- a/tests/assembly/rust-abi-arg-attr.rs
+++ b/tests/assembly/rust-abi-arg-attr.rs
@@ -51,10 +51,7 @@ enum Ordering {
}
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-fn three_way_compare<T: Copy>(lhs: T, rhs: T) -> Ordering {
- loop {}
-}
+fn three_way_compare<T: Copy>(lhs: T, rhs: T) -> Ordering;
// ^^^^^ core
diff --git a/tests/rustdoc/const-intrinsic.rs b/tests/rustdoc/const-intrinsic.rs
index 8444d4a3aa7..7dedb083b7d 100644
--- a/tests/rustdoc/const-intrinsic.rs
+++ b/tests/rustdoc/const-intrinsic.rs
@@ -9,19 +9,13 @@
#[stable(since="1.0.0", feature="rust1")]
#[rustc_const_stable(feature = "const_transmute", since = "1.56.0")]
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-pub const unsafe fn transmute<T, U>(_: T) -> U {
- loop {}
-}
+pub const unsafe fn transmute<T, U>(_: T) -> U;
//@ has 'foo/fn.unreachable.html'
//@ has - '//pre[@class="rust item-decl"]' 'pub unsafe fn unreachable() -> !'
#[stable(since="1.0.0", feature="rust1")]
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-pub unsafe fn unreachable() -> ! {
- loop {}
-}
+pub unsafe fn unreachable() -> !;
extern "C" {
//@ has 'foo/fn.needs_drop.html'
diff --git a/tests/rustdoc/safe-intrinsic.rs b/tests/rustdoc/safe-intrinsic.rs
index 1edc1d9f79b..0d2ee89415d 100644
--- a/tests/rustdoc/safe-intrinsic.rs
+++ b/tests/rustdoc/safe-intrinsic.rs
@@ -11,14 +11,8 @@ trait Sized {}
//@ has 'foo/fn.abort.html'
//@ has - '//pre[@class="rust item-decl"]' 'pub fn abort() -> !'
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-pub fn abort() -> ! {
- loop {}
-}
+pub fn abort() -> !;
//@ has 'foo/fn.unreachable.html'
//@ has - '//pre[@class="rust item-decl"]' 'pub unsafe fn unreachable() -> !'
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-pub unsafe fn unreachable() -> ! {
- loop {}
-}
+pub unsafe fn unreachable() -> !;
diff --git a/tests/ui-fulldeps/stable-mir/check_intrinsics.rs b/tests/ui-fulldeps/stable-mir/check_intrinsics.rs
index 2f772b97886..07a2a62e066 100644
--- a/tests/ui-fulldeps/stable-mir/check_intrinsics.rs
+++ b/tests/ui-fulldeps/stable-mir/check_intrinsics.rs
@@ -51,13 +51,11 @@ fn test_intrinsics() -> ControlFlow<()> {
/// This check is unfortunately tight to the implementation of intrinsics.
///
-/// We want to ensure that StableMIR can handle intrinsics with and without fallback body.
+/// We want to ensure that StableMIR can handle intrinsics with and without fallback body:
+/// for intrinsics without a body, obviously we cannot expose anything.
///
/// If by any chance this test breaks because you changed how an intrinsic is implemented, please
/// update the test to invoke a different intrinsic.
-///
-/// In StableMIR, we only expose intrinsic body if they are not marked with
-/// `rustc_intrinsic_must_be_overridden`.
fn check_instance(instance: &Instance) {
assert_eq!(instance.kind, InstanceKind::Intrinsic);
let name = instance.intrinsic_name().unwrap();
diff --git a/tests/ui/error-codes/E0094.rs b/tests/ui/error-codes/E0094.rs
index da59d3decac..2067179b26a 100644
--- a/tests/ui/error-codes/E0094.rs
+++ b/tests/ui/error-codes/E0094.rs
@@ -1,10 +1,7 @@
#![feature(intrinsics)]
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-fn size_of<T, U>() -> usize {
- //~^ ERROR E0094
- loop {}
-}
+fn size_of<T, U>() -> usize;
+//~^ ERROR E0094
fn main() {}
diff --git a/tests/ui/error-codes/E0094.stderr b/tests/ui/error-codes/E0094.stderr
index e45cc0ea063..da29987f8b1 100644
--- a/tests/ui/error-codes/E0094.stderr
+++ b/tests/ui/error-codes/E0094.stderr
@@ -1,7 +1,7 @@
error[E0094]: intrinsic has wrong number of type parameters: found 2, expected 1
- --> $DIR/E0094.rs:5:11
+ --> $DIR/E0094.rs:4:11
|
-LL | fn size_of<T, U>() -> usize {
+LL | fn size_of<T, U>() -> usize;
| ^^^^^^ expected 1 type parameter
error: aborting due to 1 previous error
diff --git a/tests/ui/error-codes/E0308.rs b/tests/ui/error-codes/E0308.rs
index f8f93d49a8e..c27d4245471 100644
--- a/tests/ui/error-codes/E0308.rs
+++ b/tests/ui/error-codes/E0308.rs
@@ -2,10 +2,7 @@
#![feature(rustc_attrs)]
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-fn size_of<T>() {
- //~^ ERROR E0308
- loop {}
-}
+fn size_of<T>();
+//~^ ERROR E0308
fn main() {}
diff --git a/tests/ui/error-codes/E0308.stderr b/tests/ui/error-codes/E0308.stderr
index 77e5c06e06a..a1077481a81 100644
--- a/tests/ui/error-codes/E0308.stderr
+++ b/tests/ui/error-codes/E0308.stderr
@@ -1,7 +1,7 @@
error[E0308]: intrinsic has wrong type
- --> $DIR/E0308.rs:6:16
+ --> $DIR/E0308.rs:5:16
|
-LL | fn size_of<T>() {
+LL | fn size_of<T>();
| ^ expected `usize`, found `()`
|
= note: expected signature `fn() -> usize`
diff --git a/tests/ui/intrinsics/always-gets-overridden.rs b/tests/ui/intrinsics/always-gets-overridden.rs
index 2fb64f96d83..aaac5415c21 100644
--- a/tests/ui/intrinsics/always-gets-overridden.rs
+++ b/tests/ui/intrinsics/always-gets-overridden.rs
@@ -1,5 +1,5 @@
-//! Check that `vtable_size` gets overridden by llvm backend even if there is no
-//! `rustc_intrinsic_must_be_overridden` attribute on this usage.
+//! Check that `vtable_size` gets overridden by llvm backend even if there is a
+//! fallback body.
#![feature(intrinsics)]
//@run-pass
diff --git a/tests/ui/repr/16-bit-repr-c-enum.rs b/tests/ui/repr/16-bit-repr-c-enum.rs
index 011076882d2..8c2d2fafce0 100644
--- a/tests/ui/repr/16-bit-repr-c-enum.rs
+++ b/tests/ui/repr/16-bit-repr-c-enum.rs
@@ -24,10 +24,7 @@ enum Foo {
#[stable(feature = "intrinsics_for_test", since = "3.3.3")]
#[rustc_const_stable(feature = "intrinsics_for_test", since = "3.3.3")]
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-const fn size_of<T>() -> usize {
- loop {}
-}
+const fn size_of<T>() -> usize;
#[lang="sized"]
trait Sized {}
diff --git a/tests/ui/target-feature/feature-hierarchy.rs b/tests/ui/target-feature/feature-hierarchy.rs
index d62b86693c2..315ec983a19 100644
--- a/tests/ui/target-feature/feature-hierarchy.rs
+++ b/tests/ui/target-feature/feature-hierarchy.rs
@@ -21,10 +21,7 @@ impl Copy for bool {}
#[stable(feature = "test", since = "1.0.0")]
#[rustc_const_stable(feature = "test", since = "1.0.0")]
#[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
-const unsafe fn unreachable() -> ! {
- loop {}
-}
+const unsafe fn unreachable() -> !;
#[rustc_builtin_macro]
macro_rules! cfg {