remove support for extern-block const intrinsics

Author: RalfJung

compiler/rustc_attr/src/builtin.rs

@@ -273,8 +273,7 @@ pub fn find_stability(
 /// Collects stability info from `rustc_const_stable`/`rustc_const_unstable`/`rustc_promotable`
 /// attributes in `attrs`. Returns `None` if no stability attributes are found.
 ///
-/// `is_const_fn` indicates whether this is a function marked as `const`. It will always
-/// be false for intrinsics in an `extern` block!
+/// `is_const_fn` indicates whether this is a function marked as `const`.
 pub fn find_const_stability(
     sess: &Session,
     attrs: &[Attribute],
@@ -330,7 +329,7 @@ pub fn find_const_stability(
         }
     }
 
-    // Merge promotable and not_exposed_on_stable into stability info
+    // Merge promotable and const_stable_indirect into stability info
     if promotable {
         match &mut const_stab {
             Some((stab, _)) => stab.promotable = promotable,
@@ -352,10 +351,7 @@ pub fn find_const_stability(
                     })
                 }
             }
-            _ => {
-                // We ignore the `#[rustc_const_stable_indirect]` here, it should be picked up by
-                // the `default_const_unstable` logic.
-            }
+            _ => {}
         }
     }
     // Make sure if `const_stable_indirect` is present, that is recorded. Also make sure all `const

compiler/rustc_const_eval/src/const_eval/fn_queries.rs

@@ -25,15 +25,9 @@ fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness {
             hir::Constness::Const
         }
         hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.constness,
-        hir::Node::ForeignItem(hir::ForeignItem { kind: hir::ForeignItemKind::Fn(..), .. }) => {
-            // Intrinsics use `rustc_const_{un,}stable` attributes to indicate constness. All other
-            // foreign items cannot be evaluated at compile-time.
-            let is_const = if tcx.intrinsic(def_id).is_some() {
-                tcx.lookup_const_stability(def_id).is_some()
-            } else {
-                false
-            };
-            if is_const { hir::Constness::Const } else { hir::Constness::NotConst }
+        hir::Node::ForeignItem(_) => {
+            // Foreign items cannot be evaluated at compile-time.
+            hir::Constness::NotConst
         }
         hir::Node::Expr(e) if let hir::ExprKind::Closure(c) = e.kind => c.constness,
         _ => {

compiler/rustc_passes/src/stability.rs

@@ -106,7 +106,6 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
         def_id: LocalDefId,
         item_sp: Span,
         fn_sig: Option<&'tcx hir::FnSig<'tcx>>,
-        is_foreign_item: bool,
         kind: AnnotationKind,
         inherit_deprecation: InheritDeprecation,
         inherit_const_stability: InheritConstStability,
@@ -175,11 +174,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
         // implied), check if the function/method is const or the parent impl block is const.
         if let Some(fn_sig) = fn_sig
             && !fn_sig.header.is_const()
-            // We have to exclude foreign items as they might be intrinsics. Sadly we can't check
-            // their ABI; `fn_sig.abi` is *not* correct for foreign functions.
-            && !is_foreign_item
             && const_stab.is_some()
-            && (!self.in_trait_impl || !self.tcx.is_const_fn(def_id.to_def_id()))
         {
             self.tcx.dcx().emit_err(errors::MissingConstErr { fn_sig_span: fn_sig.span });
         }
@@ -398,7 +393,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
                         ctor_def_id,
                         i.span,
                         None,
-                        /* is_foreign_item */ false,
                         AnnotationKind::Required,
                         InheritDeprecation::Yes,
                         InheritConstStability::No,
@@ -417,7 +411,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
             i.owner_id.def_id,
             i.span,
             fn_sig,
-            /* is_foreign_item */ false,
             kind,
             InheritDeprecation::Yes,
             const_stab_inherit,
@@ -437,7 +430,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
             ti.owner_id.def_id,
             ti.span,
             fn_sig,
-            /* is_foreign_item */ false,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -461,7 +453,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
             ii.owner_id.def_id,
             ii.span,
             fn_sig,
-            /* is_foreign_item */ false,
             kind,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -477,7 +468,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
             var.def_id,
             var.span,
             None,
-            /* is_foreign_item */ false,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -488,7 +478,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
                         ctor_def_id,
                         var.span,
                         None,
-                        /* is_foreign_item */ false,
                         AnnotationKind::Required,
                         InheritDeprecation::Yes,
                         InheritConstStability::No,
@@ -507,7 +496,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
             s.def_id,
             s.span,
             None,
-            /* is_foreign_item */ false,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -527,7 +515,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
             i.owner_id.def_id,
             i.span,
             fn_sig,
-            /* is_foreign_item */ true,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -550,7 +537,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
             p.def_id,
             p.span,
             None,
-            /* is_foreign_item */ false,
             kind,
             InheritDeprecation::No,
             InheritConstStability::No,
@@ -712,7 +698,6 @@ fn stability_index(tcx: TyCtxt<'_>, (): ()) -> Index {
             CRATE_DEF_ID,
             tcx.hir().span(CRATE_HIR_ID),
             None,
-            /* is_foreign_item */ false,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,

tests/rustdoc/const-intrinsic.rs

@@ -1,20 +1,26 @@
-#![feature(intrinsics)]
+#![feature(intrinsics, rustc_attrs)]
 #![feature(staged_api)]
 
 #![crate_name = "foo"]
 #![stable(since="1.0.0", feature="rust1")]
 
-extern "rust-intrinsic" {
-    //@ has 'foo/fn.transmute.html'
-    //@ has - '//pre[@class="rust item-decl"]' 'pub const unsafe extern "rust-intrinsic" fn transmute<T, U>(_: T) -> U'
-    #[stable(since="1.0.0", feature="rust1")]
-    #[rustc_const_stable(feature = "const_transmute", since = "1.56.0")]
-    pub fn transmute<T, U>(_: T) -> U;
+//@ has 'foo/fn.transmute.html'
+//@ has - '//pre[@class="rust item-decl"]' 'pub const unsafe fn transmute<T, U>(_: T) -> U'
+#[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 {}
+}
 
-    //@ has 'foo/fn.unreachable.html'
-    //@ has - '//pre[@class="rust item-decl"]' 'pub unsafe extern "rust-intrinsic" fn unreachable() -> !'
-    #[stable(since="1.0.0", feature="rust1")]
-    pub fn unreachable() -> !;
+//@ 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 {}
 }
 
 extern "C" {

tests/ui/closures/coerce-unsafe-to-closure.stderr

@@ -1,12 +1,12 @@
-error[E0277]: expected a `FnOnce(&str)` closure, found `unsafe extern "rust-intrinsic" fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
+error[E0277]: expected a `FnOnce(&str)` closure, found `unsafe fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
   --> $DIR/coerce-unsafe-to-closure.rs:2:44
    |
 LL |     let x: Option<&[u8]> = Some("foo").map(std::mem::transmute);
    |                                        --- ^^^^^^^^^^^^^^^^^^^ call the function in a closure: `|| unsafe { /* code */ }`
    |                                        |
    |                                        required by a bound introduced by this call
    |
-   = help: the trait `FnOnce(&str)` is not implemented for fn item `unsafe extern "rust-intrinsic" fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
+   = help: the trait `FnOnce(&str)` is not implemented for fn item `unsafe fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
    = note: unsafe function cannot be called generically without an unsafe block
 note: required by a bound in `Option::<T>::map`
   --> $SRC_DIR/core/src/option.rs:LL:COL

tests/ui/consts/auxiliary/unstable_intrinsic.rs

@@ -1,26 +1,11 @@
 #![feature(staged_api, rustc_attrs, intrinsics)]
 #![stable(since="1.0.0", feature = "stable")]
 
-#[stable(since="1.0.0", feature = "stable")]
-pub mod old_way {
-    extern "rust-intrinsic" {
-        #[unstable(feature = "unstable", issue = "42")]
-        pub fn size_of_val<T>(x: *const T) -> usize;
-
-        #[unstable(feature = "unstable", issue = "42")]
-        #[rustc_const_unstable(feature = "unstable", issue = "42")]
-        pub fn min_align_of_val<T>(x: *const T) -> usize;
-    }
-}
-
-#[stable(since="1.0.0", feature = "stable")]
-pub mod new_way {
-    #[unstable(feature = "unstable", issue = "42")]
-    #[rustc_intrinsic]
-    pub const unsafe fn size_of_val<T>(x: *const T) -> usize { 42 }
-
-    #[unstable(feature = "unstable", issue = "42")]
-    #[rustc_const_unstable(feature = "unstable", issue = "42")]
-    #[rustc_intrinsic]
-    pub const unsafe fn min_align_of_val<T>(x: *const T) -> usize { 42 }
-}
+#[unstable(feature = "unstable", issue = "42")]
+#[rustc_intrinsic]
+pub const unsafe fn size_of_val<T>(x: *const T) -> usize { 42 }
+
+#[unstable(feature = "unstable", issue = "42")]
+#[rustc_const_unstable(feature = "unstable", issue = "42")]
+#[rustc_intrinsic]
+pub const unsafe fn min_align_of_val<T>(x: *const T) -> usize { 42 }

tests/ui/consts/const-eval/simd/insert_extract.rs

@@ -1,6 +1,6 @@
 //@ run-pass
 #![feature(repr_simd)]
-#![feature(intrinsics)]
+#![feature(intrinsics, rustc_attrs)]
 #![feature(staged_api)]
 #![stable(feature = "foo", since = "1.3.37")]
 #![allow(non_camel_case_types)]
@@ -10,14 +10,18 @@
 #[repr(simd)] struct u16x2([u16; 2]);
 #[repr(simd)] struct f32x4([f32; 4]);
 
-extern "rust-intrinsic" {
-    #[stable(feature = "foo", since = "1.3.37")]
-    #[rustc_const_stable(feature = "foo", since = "1.3.37")]
-    fn simd_insert<T, U>(x: T, idx: u32, val: U) -> T;
+#[stable(feature = "foo", since = "1.3.37")]
+#[rustc_const_stable(feature = "foo", since = "1.3.37")]
+#[rustc_intrinsic]
+const unsafe fn simd_insert<T, U>(_x: T, _idx: u32, _val: U) -> T {
+    unimplemented!()
+}
 
-    #[stable(feature = "foo", since = "1.3.37")]
-    #[rustc_const_stable(feature = "foo", since = "1.3.37")]
-    fn simd_extract<T, U>(x: T, idx: u32) -> U;
+#[stable(feature = "foo", since = "1.3.37")]
+#[rustc_const_stable(feature = "foo", since = "1.3.37")]
+#[rustc_intrinsic]
+const unsafe fn simd_extract<T, U>(_x: T, _idx: u32) -> U {
+    unimplemented!()
 }
 
 fn main() {

tests/ui/consts/const-unstable-intrinsic.rs

@@ -14,63 +14,39 @@ fn main() {
 const fn const_main() {
     let x = 42;
     unsafe {
-        unstable_intrinsic::old_way::size_of_val(&x);
-        //~^ERROR: unstable library feature `unstable`
-        //~|ERROR: cannot call non-const intrinsic
-        unstable_intrinsic::old_way::min_align_of_val(&x);
-        //~^ERROR: unstable library feature `unstable`
-        //~|ERROR: not yet stable as a const intrinsic
-        unstable_intrinsic::new_way::size_of_val(&x);
+        unstable_intrinsic::size_of_val(&x);
         //~^ERROR: unstable library feature `unstable`
         //~|ERROR: cannot be (indirectly) exposed to stable
-        unstable_intrinsic::new_way::min_align_of_val(&x);
+        unstable_intrinsic::min_align_of_val(&x);
         //~^ERROR: unstable library feature `unstable`
         //~|ERROR: not yet stable as a const intrinsic
 
-        old_way::size_of_val(&x);
-        //~^ERROR: cannot call non-const intrinsic
-        old_way::min_align_of_val(&x);
-        //~^ERROR: cannot use `#[feature(local)]`
-        new_way::size_of_val(&x);
+        size_of_val(&x);
         //~^ERROR: cannot be (indirectly) exposed to stable
-        new_way::min_align_of_val(&x);
+        min_align_of_val(&x);
         //~^ERROR: cannot use `#[feature(local)]`
     }
 }
 
-#[stable(since="1.0.0", feature = "stable")]
-pub mod old_way {
-    extern "rust-intrinsic" {
-        #[unstable(feature = "local", issue = "42")]
-        pub fn size_of_val<T>(x: *const T) -> usize;
-
-        #[unstable(feature = "local", issue = "42")]
-        #[rustc_const_unstable(feature = "local", issue = "42")]
-        pub fn min_align_of_val<T>(x: *const T) -> usize;
-    }
-}
-
-#[stable(since="1.0.0", feature = "stable")]
-pub mod new_way {
-    #[unstable(feature = "local", issue = "42")]
-    #[rustc_intrinsic]
-    pub const unsafe fn size_of_val<T>(x: *const T) -> usize { 42 }
+#[unstable(feature = "local", issue = "42")]
+#[rustc_intrinsic]
+pub const unsafe fn size_of_val<T>(x: *const T) -> usize { 42 }
 
-    #[unstable(feature = "local", issue = "42")]
-    #[rustc_const_unstable(feature = "local", issue = "42")]
-    #[rustc_intrinsic]
-    pub const unsafe fn min_align_of_val<T>(x: *const T) -> usize { 42 }
-}
+#[unstable(feature = "local", issue = "42")]
+#[rustc_const_unstable(feature = "local", issue = "42")]
+#[rustc_intrinsic]
+pub const unsafe fn min_align_of_val<T>(x: *const T) -> usize { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
 #[inline]
 pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
     // Const stability attributes are not inherited from parent items.
-    extern "rust-intrinsic" {
-        fn copy<T>(src: *const T, dst: *mut T, count: usize);
+    #[rustc_intrinsic]
+    const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
+        unimplemented!()
     }
 
     unsafe { copy(src, dst, count) }
-    //~^ ERROR cannot call non-const intrinsic
+    //~^ ERROR cannot be (indirectly) exposed to stable
 }