Auto merge of #88618 - m-ou-se:rollup-6tss5z6, r=m-ou-se

Rollup of 7 pull requests

Successful merges:

 - #88202 (Add an example for deriving PartialOrd on enums)
 - #88483 (Fix LLVM libunwind build for non-musl targets)
 - #88507 (Add test case for using `slice::fill` with MaybeUninit)
 - #88557 (small const generics cleanup)
 - #88579 (remove redundant / misplaced sentence from docs)
 - #88610 (Update outdated docs of array::IntoIter::new.)
 - #88613 (Update primitive docs for rust 2021.)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -820,10 +820,10 @@ fn contains_illegal_self_type_reference<'tcx, T: TypeFoldable<'tcx>>(
             }
         }
 
-        fn visit_const(&mut self, ct: &ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
-            // First check if the type of this constant references `Self`.
-            self.visit_ty(ct.ty)?;
-
+        fn visit_unevaluated_const(
+            &mut self,
+            uv: ty::Unevaluated<'tcx>,
+        ) -> ControlFlow<Self::BreakTy> {
             // Constants can only influence object safety if they reference `Self`.
             // This is only possible for unevaluated constants, so we walk these here.
             //
@@ -837,7 +837,7 @@ fn contains_illegal_self_type_reference<'tcx, T: TypeFoldable<'tcx>>(
             // This shouldn't really matter though as we can't really use any
             // constants which are not considered const evaluatable.
             use rustc_middle::mir::abstract_const::Node;
-            if let Ok(Some(ct)) = AbstractConst::from_const(self.tcx, ct) {
+            if let Ok(Some(ct)) = AbstractConst::new(self.tcx, uv.shrink()) {
                 const_evaluatable::walk_abstract_const(self.tcx, ct, |node| match node.root() {
                     Node::Leaf(leaf) => {
                         let leaf = leaf.subst(self.tcx, ct.substs);
@@ -852,31 +852,6 @@ fn contains_illegal_self_type_reference<'tcx, T: TypeFoldable<'tcx>>(
                 ControlFlow::CONTINUE
             }
         }
-
-        fn visit_predicate(&mut self, pred: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> {
-            if let ty::PredicateKind::ConstEvaluatable(ct) = pred.kind().skip_binder() {
-                // FIXME(generic_const_exprs): We should probably deduplicate the logic for
-                // `AbstractConst`s here, it might make sense to change `ConstEvaluatable` to
-                // take a `ty::Const` instead.
-                use rustc_middle::mir::abstract_const::Node;
-                if let Ok(Some(ct)) = AbstractConst::new(self.tcx, ct) {
-                    const_evaluatable::walk_abstract_const(self.tcx, ct, |node| match node.root() {
-                        Node::Leaf(leaf) => {
-                            let leaf = leaf.subst(self.tcx, ct.substs);
-                            self.visit_const(leaf)
-                        }
-                        Node::Cast(_, _, ty) => self.visit_ty(ty),
-                        Node::Binop(..) | Node::UnaryOp(..) | Node::FunctionCall(_, _) => {
-                            ControlFlow::CONTINUE
-                        }
-                    })
-                } else {
-                    ControlFlow::CONTINUE
-                }
-            } else {
-                pred.super_visit_with(self)
-            }
-        }
     }
 
     value

compiler/rustc_typeck/src/outlives/implicit_infer.rs

@@ -120,7 +120,7 @@ fn insert_required_predicates_to_be_wf<'tcx>(
     // Luckily the only types contained in default substs are type
     // parameters which don't matter here.
     //
-    // FIXME(const_generics): Once more complex const parameter types
+    // FIXME(adt_const_params): Once complex const parameter types
     // are allowed, this might be incorrect. I think that we will still be
     // fine, as all outlives relations of the const param types should also
     // be part of the adt containing it, but we should still both update the

library/core/src/array/iter.rs

@@ -37,7 +37,7 @@ impl<T, const N: usize> IntoIter<T, N> {
     /// Creates a new iterator over the given `array`.
     ///
     /// *Note*: this method might be deprecated in the future,
-    /// after [`IntoIterator` is implemented for arrays][array-into-iter].
+    /// since [`IntoIterator`] is now implemented for arrays.
     ///
     /// # Examples
     ///
@@ -48,8 +48,13 @@ impl<T, const N: usize> IntoIter<T, N> {
     ///     // The type of `value` is an `i32` here, instead of `&i32`
     ///     let _: i32 = value;
     /// }
+    ///
+    /// // Since Rust 1.53, arrays implement IntoIterator directly:
+    /// for value in [1, 2, 3, 4, 5] {
+    ///     // The type of `value` is an `i32` here, instead of `&i32`
+    ///     let _: i32 = value;
+    /// }
     /// ```
-    /// [array-into-iter]: https://github.com/rust-lang/rust/pull/65819
     #[stable(feature = "array_value_iter", since = "1.51.0")]
     pub fn new(array: [T; N]) -> Self {
         // SAFETY: The transmute here is actually safe. The docs of `MaybeUninit`

library/core/src/cmp.rs

@@ -660,6 +660,18 @@ impl<T: Clone> Clone for Reverse<T> {
 /// This trait can be used with `#[derive]`. When `derive`d on structs, it will produce a
 /// [lexicographic](https://en.wikipedia.org/wiki/Lexicographic_order) ordering based on the top-to-bottom declaration order of the struct's members.
 /// When `derive`d on enums, variants are ordered by their top-to-bottom discriminant order.
+/// This means variants at the top are less than variants at the bottom.
+/// Here's an example:
+///
+/// ```
+/// #[derive(PartialEq, PartialOrd)]
+/// enum Size {
+///     Small,
+///     Large,
+/// }
+///
+/// assert!(Size::Small < Size::Large);
+/// ```
 ///
 /// ## Lexicographical comparison
 ///

library/core/src/ptr/mod.rs

@@ -182,10 +182,6 @@ mod mut_ptr;
 /// // Ensure that the last item was dropped.
 /// assert!(weak.upgrade().is_none());
 /// ```
-///
-/// Notice that the compiler performs this copy automatically when dropping packed structs,
-/// i.e., you do not usually have to worry about such issues unless you call `drop_in_place`
-/// manually.
 #[stable(feature = "drop_in_place", since = "1.8.0")]
 #[lang = "drop_in_place"]
 #[allow(unconditional_recursion)]

library/core/tests/slice.rs

@@ -1,5 +1,6 @@
 use core::cell::Cell;
 use core::cmp::Ordering;
+use core::mem::MaybeUninit;
 use core::result::Result::{Err, Ok};
 
 #[test]
@@ -2144,3 +2145,10 @@ fn test_slice_run_destructors() {
 
     assert_eq!(x.get(), 1);
 }
+
+#[test]
+fn test_slice_fill_with_uninit() {
+    // This should not UB. See #87891
+    let mut a = [MaybeUninit::<u8>::uninit(); 10];
+    a.fill(MaybeUninit::uninit());
+}

library/std/src/primitive_docs.rs

@@ -581,6 +581,8 @@ mod prim_pointer {}
 /// might be made consistent to the behavior of later editions.
 ///
 /// ```rust,edition2018
+/// // Rust 2015 and 2018:
+///
 /// # #![allow(array_into_iter)] // override our `deny(warnings)`
 /// let array: [i32; 3] = [0; 3];
 ///
@@ -604,11 +606,13 @@ mod prim_pointer {}
 /// }
 /// ```
 ///
-/// Starting in the 2021 edition, `array.into_iter()` will use `IntoIterator` normally to iterate
+/// Starting in the 2021 edition, `array.into_iter()` uses `IntoIterator` normally to iterate
 /// by value, and `iter()` should be used to iterate by reference like previous editions.
 ///
-/// ```rust,edition2021,ignore
-/// # // FIXME: ignored because 2021 testing is still unstable
+#[cfg_attr(bootstrap, doc = "```rust,edition2021,ignore")]
+#[cfg_attr(not(bootstrap), doc = "```rust,edition2021")]
+/// // Rust 2021:
+///
 /// let array: [i32; 3] = [0; 3];
 ///
 /// // This iterates by reference:
@@ -631,12 +635,12 @@ mod prim_pointer {}
 /// avoid the `into_iter` syntax on those editions. If an edition update is not
 /// viable/desired, there are multiple alternatives:
 /// * use `iter`, equivalent to the old behavior, creating references
-/// * use [`array::IntoIter`], equivalent to the post-2021 behavior (Rust 1.51+)
+/// * use [`IntoIterator::into_iter`], equivalent to the post-2021 behavior (Rust 1.53+)
 /// * replace `for ... in array.into_iter() {` with `for ... in array {`,
 ///   equivalent to the post-2021 behavior (Rust 1.53+)
 ///
 /// ```rust,edition2018
-/// use std::array::IntoIter;
+/// // Rust 2015 and 2018:
 ///
 /// let array: [i32; 3] = [0; 3];
 ///
@@ -647,7 +651,7 @@ mod prim_pointer {}
 /// }
 ///
 /// // This iterates by value:
-/// for item in IntoIter::new(array) {
+/// for item in IntoIterator::into_iter(array) {
 ///     let x: i32 = item;
 ///     println!("{}", x);
 /// }
@@ -660,7 +664,7 @@ mod prim_pointer {}
 ///
 /// // IntoIter can also start a chain.
 /// // This iterates by value:
-/// for item in IntoIter::new(array).enumerate() {
+/// for item in IntoIterator::into_iter(array).enumerate() {
 ///     let (i, x): (usize, i32) = item;
 ///     println!("array[{}] = {}", i, x);
 /// }

src/bootstrap/compile.rs

@@ -142,6 +142,14 @@ fn copy_and_stamp(
     target_deps.push((target, dependency_type));
 }
 
+fn copy_llvm_libunwind(builder: &Builder<'_>, target: TargetSelection, libdir: &Path) -> PathBuf {
+    let libunwind_path = builder.ensure(native::Libunwind { target });
+    let libunwind_source = libunwind_path.join("libunwind.a");
+    let libunwind_target = libdir.join("libunwind.a");
+    builder.copy(&libunwind_source, &libunwind_target);
+    libunwind_target
+}
+
 /// Copies third party objects needed by various targets.
 fn copy_third_party_objects(
     builder: &Builder<'_>,
@@ -167,6 +175,15 @@ fn copy_third_party_objects(
         );
     }
 
+    if target == "x86_64-fortanix-unknown-sgx"
+        || builder.config.llvm_libunwind == LlvmLibunwind::InTree
+            && (target.contains("linux") || target.contains("fuchsia"))
+    {
+        let libunwind_path =
+            copy_llvm_libunwind(builder, target, &builder.sysroot_libdir(*compiler, target));
+        target_deps.push((libunwind_path, DependencyType::Target));
+    }
+
     target_deps
 }
 
@@ -208,6 +225,9 @@ fn copy_self_contained_objects(
             builder.copy(&src, &target);
             target_deps.push((target, DependencyType::TargetSelfContained));
         }
+
+        let libunwind_path = copy_llvm_libunwind(builder, target, &libdir_self_contained);
+        target_deps.push((libunwind_path, DependencyType::TargetSelfContained));
     } else if target.ends_with("-wasi") {
         let srcdir = builder
             .wasi_root(target)
@@ -234,18 +254,6 @@ fn copy_self_contained_objects(
         }
     }
 
-    if target.contains("musl")
-        || target.contains("x86_64-fortanix-unknown-sgx")
-        || builder.config.llvm_libunwind == LlvmLibunwind::InTree
-            && (target.contains("linux") || target.contains("fuchsia"))
-    {
-        let libunwind_path = builder.ensure(native::Libunwind { target });
-        let libunwind_source = libunwind_path.join("libunwind.a");
-        let libunwind_target = libdir_self_contained.join("libunwind.a");
-        builder.copy(&libunwind_source, &libunwind_target);
-        target_deps.push((libunwind_target, DependencyType::TargetSelfContained));
-    }
-
     target_deps
 }