Rollup of 8 pull requests

compiler/rustc_attr_parsing/src/attributes/crate_level.rs

@@ -283,3 +283,12 @@ impl<S: Stage> NoArgsAttributeParser<S> for RustcPreserveUbChecksParser {
     const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Crate)]);
     const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::RustcPreserveUbChecks;
 }
+
+pub(crate) struct RustcNoImplicitBoundsParser;
+
+impl<S: Stage> NoArgsAttributeParser<S> for RustcNoImplicitBoundsParser {
+    const PATH: &[Symbol] = &[sym::rustc_no_implicit_bounds];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Crate)]);
+    const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::RustcNoImplicitBounds;
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -281,6 +281,7 @@ attribute_parsers!(
         Single<WithoutArgs<RustcMainParser>>,
         Single<WithoutArgs<RustcNeverReturnsNullPointerParser>>,
         Single<WithoutArgs<RustcNoImplicitAutorefsParser>>,
+        Single<WithoutArgs<RustcNoImplicitBoundsParser>>,
         Single<WithoutArgs<RustcNonConstTraitMethodParser>>,
         Single<WithoutArgs<RustcNounwindParser>>,
         Single<WithoutArgs<RustcOffloadKernelParser>>,

compiler/rustc_borrowck/src/lib.rs

@@ -121,6 +121,11 @@ fn mir_borrowck(
     let (input_body, _) = tcx.mir_promoted(def);
     debug!("run query mir_borrowck: {}", tcx.def_path_str(def));
 
+    // We should eagerly check stalled coroutine obligations from HIR typeck.
+    // Not doing so leads to silent normalization failures later, which will
+    // fail to register opaque types in the next solver.
+    tcx.check_coroutine_obligations(def)?;
+
     let input_body: &Body<'_> = &input_body.borrow();
     if let Some(guar) = input_body.tainted_by_errors {
         debug!("Skipping borrowck because of tainted body");

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -1177,6 +1177,9 @@ pub enum AttributeKind {
     /// Represents `#[rustc_no_implicit_autorefs]`
     RustcNoImplicitAutorefs,
 
+    /// Represents `#[rustc_no_implicit_bounds]`
+    RustcNoImplicitBounds,
+
     /// Represents `#[rustc_non_const_trait_method]`.
     RustcNonConstTraitMethod,
 

compiler/rustc_hir/src/attrs/encode_cross_crate.rs

@@ -137,6 +137,7 @@ impl AttributeKind {
             RustcMustImplementOneOf { .. } => No,
             RustcNeverReturnsNullPointer => Yes,
             RustcNoImplicitAutorefs => Yes,
+            RustcNoImplicitBounds => No,
             RustcNonConstTraitMethod => No, // should be reported via other queries like `constness`
             RustcNounwind => No,
             RustcObjcClass { .. } => No,

compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs

@@ -4,15 +4,16 @@ use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::codes::*;
 use rustc_errors::struct_span_code_err;
 use rustc_hir as hir;
-use rustc_hir::PolyTraitRef;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
+use rustc_hir::{PolyTraitRef, find_attr};
 use rustc_middle::bug;
 use rustc_middle::ty::{
     self as ty, IsSuggestable, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
     TypeVisitor, Upcast,
 };
-use rustc_span::{ErrorGuaranteed, Ident, Span, kw, sym};
+use rustc_span::{ErrorGuaranteed, Ident, Span, kw};
 use rustc_trait_selection::traits;
 use smallvec::SmallVec;
 use tracing::{debug, instrument};
@@ -170,7 +171,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let tcx = self.tcx();
 
         // Skip adding any default bounds if `#![rustc_no_implicit_bounds]`
-        if tcx.has_attr(CRATE_DEF_ID, sym::rustc_no_implicit_bounds) {
+        if find_attr!(tcx.get_all_attrs(CRATE_DEF_ID), AttributeKind::RustcNoImplicitBounds) {
             return;
         }
 
@@ -284,7 +285,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         context: ImpliedBoundsContext<'tcx>,
     ) -> bool {
         let collected = collect_bounds(hir_bounds, context, trait_def_id);
-        !self.tcx().has_attr(CRATE_DEF_ID, sym::rustc_no_implicit_bounds) && !collected.any()
+        !find_attr!(self.tcx().get_all_attrs(CRATE_DEF_ID), AttributeKind::RustcNoImplicitBounds)
+            && !collected.any()
     }
 
     fn reject_duplicate_relaxed_bounds(&self, relaxed_bounds: SmallVec<[&PolyTraitRef<'_>; 1]>) {

compiler/rustc_interface/src/passes.rs

@@ -1116,18 +1116,14 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
             {
                 tcx.ensure_ok().mir_drops_elaborated_and_const_checked(def_id);
             }
-            if tcx.is_coroutine(def_id.to_def_id()) {
-                tcx.ensure_ok().mir_coroutine_witnesses(def_id);
-                let _ = tcx.ensure_ok().check_coroutine_obligations(
-                    tcx.typeck_root_def_id(def_id.to_def_id()).expect_local(),
+            if tcx.is_coroutine(def_id.to_def_id())
+                && (!tcx.is_async_drop_in_place_coroutine(def_id.to_def_id()))
+            {
+                // Eagerly check the unsubstituted layout for cycles.
+                tcx.ensure_ok().layout_of(
+                    ty::TypingEnv::post_analysis(tcx, def_id.to_def_id())
+                        .as_query_input(tcx.type_of(def_id).instantiate_identity()),
                 );
-                if !tcx.is_async_drop_in_place_coroutine(def_id.to_def_id()) {
-                    // Eagerly check the unsubstituted layout for cycles.
-                    tcx.ensure_ok().layout_of(
-                        ty::TypingEnv::post_analysis(tcx, def_id.to_def_id())
-                            .as_query_input(tcx.type_of(def_id).instantiate_identity()),
-                    );
-                }
             }
         });
     });

compiler/rustc_middle/src/ty/context/tls.rs

@@ -16,8 +16,7 @@ pub struct ImplicitCtxt<'a, 'tcx> {
     /// The current `TyCtxt`.
     pub tcx: TyCtxt<'tcx>,
 
-    /// The current query job, if any. This is updated by `JobOwner::start` in
-    /// `ty::query::plumbing` when executing a query.
+    /// The current query job, if any.
     pub query: Option<QueryJobId>,
 
     /// Used to prevent queries from calling too deeply.

compiler/rustc_passes/src/check_attr.rs

@@ -330,6 +330,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::RustcMir(_)
                     | AttributeKind::RustcNeverReturnsNullPointer
                     | AttributeKind::RustcNoImplicitAutorefs
+                    | AttributeKind::RustcNoImplicitBounds
                     | AttributeKind::RustcNonConstTraitMethod
                     | AttributeKind::RustcNounwind
                     | AttributeKind::RustcObjcClass { .. }
@@ -413,7 +414,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             // crate-level attrs, are checked below
                             | sym::feature
                             | sym::register_tool
-                            | sym::rustc_no_implicit_bounds
                             | sym::test_runner,
                             ..
                         ] => {}

compiler/rustc_query_impl/src/execution.rs

@@ -83,14 +83,18 @@ pub(crate) fn gather_active_jobs_inner<'tcx, K: Copy>(
     Some(())
 }
 
-/// A type representing the responsibility to execute the job in the `job` field.
-/// This will poison the relevant query if dropped.
-struct JobOwner<'tcx, K>
+/// Guard object representing the responsibility to execute a query job and
+/// mark it as completed.
+///
+/// This will poison the relevant query key if it is dropped without calling
+/// [`Self::complete`].
+struct ActiveJobGuard<'tcx, K>
 where
     K: Eq + Hash + Copy,
 {
     state: &'tcx QueryState<'tcx, K>,
     key: K,
+    key_hash: u64,
 }
 
 #[cold]
@@ -137,20 +141,19 @@ fn handle_cycle_error<'tcx, C: QueryCache, const FLAGS: QueryFlags>(
     }
 }
 
-impl<'tcx, K> JobOwner<'tcx, K>
+impl<'tcx, K> ActiveJobGuard<'tcx, K>
 where
     K: Eq + Hash + Copy,
 {
     /// Completes the query by updating the query cache with the `result`,
-    /// signals the waiter and forgets the JobOwner, so it won't poison the query
-    fn complete<C>(self, cache: &C, key_hash: u64, result: C::Value, dep_node_index: DepNodeIndex)
+    /// signals the waiter, and forgets the guard so it won't poison the query.
+    fn complete<C>(self, cache: &C, result: C::Value, dep_node_index: DepNodeIndex)
     where
         C: QueryCache<Key = K>,
     {
-        let key = self.key;
-        let state = self.state;
-
-        // Forget ourself so our destructor won't poison the query
+        // Forget ourself so our destructor won't poison the query.
+        // (Extract fields by value first to make sure we don't leak anything.)
+        let Self { state, key, key_hash }: Self = self;
         mem::forget(self);
 
         // Mark as complete before we remove the job from the active state
@@ -174,19 +177,18 @@ where
     }
 }
 
-impl<'tcx, K> Drop for JobOwner<'tcx, K>
+impl<'tcx, K> Drop for ActiveJobGuard<'tcx, K>
 where
     K: Eq + Hash + Copy,
 {
     #[inline(never)]
     #[cold]
     fn drop(&mut self) {
         // Poison the query so jobs waiting on it panic.
-        let state = self.state;
+        let Self { state, key, key_hash } = *self;
         let job = {
-            let key_hash = sharded::make_hash(&self.key);
             let mut shard = state.active.lock_shard_by_hash(key_hash);
-            match shard.find_entry(key_hash, equivalent_key(&self.key)) {
+            match shard.find_entry(key_hash, equivalent_key(&key)) {
                 Err(_) => panic!(),
                 Ok(occupied) => {
                     let ((key, value), vacant) = occupied.remove();
@@ -342,11 +344,13 @@ fn execute_job<'tcx, C: QueryCache, const FLAGS: QueryFlags, const INCR: bool>(
     id: QueryJobId,
     dep_node: Option<DepNode>,
 ) -> (C::Value, Option<DepNodeIndex>) {
-    // Use `JobOwner` so the query will be poisoned if executing it panics.
-    let job_owner = JobOwner { state, key };
+    // Set up a guard object that will automatically poison the query if a
+    // panic occurs while executing the query (or any intermediate plumbing).
+    let job_guard = ActiveJobGuard { state, key, key_hash };
 
     debug_assert_eq!(qcx.tcx.dep_graph.is_fully_enabled(), INCR);
 
+    // Delegate to another function to actually execute the query job.
     let (result, dep_node_index) = if INCR {
         execute_job_incr(query, qcx, qcx.tcx.dep_graph.data().unwrap(), key, dep_node, id)
     } else {
@@ -388,7 +392,9 @@ fn execute_job<'tcx, C: QueryCache, const FLAGS: QueryFlags, const INCR: bool>(
             }
         }
     }
-    job_owner.complete(cache, key_hash, result, dep_node_index);
+
+    // Tell the guard to perform completion bookkeeping, and also to not poison the query.
+    job_guard.complete(cache, result, dep_node_index);
 
     (result, Some(dep_node_index))
 }

library/core/src/cell.rs

@@ -689,6 +689,30 @@ impl<T: CoerceUnsized<U>, U> CoerceUnsized<Cell<U>> for Cell<T> {}
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<Cell<U>> for Cell<T> {}
 
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T, const N: usize> AsRef<[Cell<T>; N]> for Cell<[T; N]> {
+    #[inline]
+    fn as_ref(&self) -> &[Cell<T>; N] {
+        self.as_array_of_cells()
+    }
+}
+
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T, const N: usize> AsRef<[Cell<T>]> for Cell<[T; N]> {
+    #[inline]
+    fn as_ref(&self) -> &[Cell<T>] {
+        &*self.as_array_of_cells()
+    }
+}
+
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T> AsRef<[Cell<T>]> for Cell<[T]> {
+    #[inline]
+    fn as_ref(&self) -> &[Cell<T>] {
+        self.as_slice_of_cells()
+    }
+}
+
 impl<T> Cell<[T]> {
     /// Returns a `&[Cell<T>]` from a `&Cell<[T]>`
     ///

library/core/src/mem/maybe_uninit.rs

@@ -1532,6 +1532,56 @@ impl<T, const N: usize> MaybeUninit<[T; N]> {
     }
 }
 
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T, const N: usize> From<[MaybeUninit<T>; N]> for MaybeUninit<[T; N]> {
+    #[inline]
+    fn from(arr: [MaybeUninit<T>; N]) -> Self {
+        arr.transpose()
+    }
+}
+
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T, const N: usize> AsRef<[MaybeUninit<T>; N]> for MaybeUninit<[T; N]> {
+    #[inline]
+    fn as_ref(&self) -> &[MaybeUninit<T>; N] {
+        // SAFETY: T and MaybeUninit<T> have the same layout
+        unsafe { &*ptr::from_ref(self).cast() }
+    }
+}
+
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T, const N: usize> AsRef<[MaybeUninit<T>]> for MaybeUninit<[T; N]> {
+    #[inline]
+    fn as_ref(&self) -> &[MaybeUninit<T>] {
+        &*AsRef::<[MaybeUninit<T>; N]>::as_ref(self)
+    }
+}
+
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T, const N: usize> AsMut<[MaybeUninit<T>; N]> for MaybeUninit<[T; N]> {
+    #[inline]
+    fn as_mut(&mut self) -> &mut [MaybeUninit<T>; N] {
+        // SAFETY: T and MaybeUninit<T> have the same layout
+        unsafe { &mut *ptr::from_mut(self).cast() }
+    }
+}
+
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T, const N: usize> AsMut<[MaybeUninit<T>]> for MaybeUninit<[T; N]> {
+    #[inline]
+    fn as_mut(&mut self) -> &mut [MaybeUninit<T>] {
+        &mut *AsMut::<[MaybeUninit<T>; N]>::as_mut(self)
+    }
+}
+
+#[stable(feature = "more_conversion_trait_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T, const N: usize> From<MaybeUninit<[T; N]>> for [MaybeUninit<T>; N] {
+    #[inline]
+    fn from(arr: MaybeUninit<[T; N]>) -> Self {
+        arr.transpose()
+    }
+}
+
 impl<T, const N: usize> [MaybeUninit<T>; N] {
     /// Transposes a `[MaybeUninit<T>; N]` into a `MaybeUninit<[T; N]>`.
     ///

library/core/src/slice/iter.rs

@@ -2175,7 +2175,7 @@ unsafe impl<T> Sync for ChunksExactMut<'_, T> where T: Sync {}
 ///
 /// [`array_windows`]: slice::array_windows
 /// [slices]: slice
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug)]
 #[stable(feature = "array_windows", since = "1.94.0")]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct ArrayWindows<'a, T: 'a, const N: usize> {
@@ -2189,6 +2189,14 @@ impl<'a, T: 'a, const N: usize> ArrayWindows<'a, T, N> {
     }
 }
 
+// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
+#[stable(feature = "array_windows", since = "1.94.0")]
+impl<T, const N: usize> Clone for ArrayWindows<'_, T, N> {
+    fn clone(&self) -> Self {
+        Self { v: self.v }
+    }
+}
+
 #[stable(feature = "array_windows", since = "1.94.0")]
 impl<'a, T, const N: usize> Iterator for ArrayWindows<'a, T, N> {
     type Item = &'a [T; N];
@@ -2224,6 +2232,14 @@ impl<'a, T, const N: usize> Iterator for ArrayWindows<'a, T, N> {
     fn last(self) -> Option<Self::Item> {
         self.v.last_chunk()
     }
+
+    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
+        // SAFETY: since the caller guarantees that `idx` is in bounds,
+        // which means that `idx` cannot overflow an `isize`, and the
+        // "slice" created by `cast_array` is a subslice of `self.v`
+        // thus is guaranteed to be valid for the lifetime `'a` of `self.v`.
+        unsafe { &*self.v.as_ptr().add(idx).cast_array() }
+    }
 }
 
 #[stable(feature = "array_windows", since = "1.94.0")]
@@ -2252,6 +2268,22 @@ impl<T, const N: usize> ExactSizeIterator for ArrayWindows<'_, T, N> {
     }
 }
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T, const N: usize> TrustedLen for ArrayWindows<'_, T, N> {}
+
+#[stable(feature = "array_windows", since = "1.94.0")]
+impl<T, const N: usize> FusedIterator for ArrayWindows<'_, T, N> {}
+
+#[doc(hidden)]
+#[unstable(feature = "trusted_random_access", issue = "none")]
+unsafe impl<T, const N: usize> TrustedRandomAccess for ArrayWindows<'_, T, N> {}
+
+#[doc(hidden)]
+#[unstable(feature = "trusted_random_access", issue = "none")]
+unsafe impl<T, const N: usize> TrustedRandomAccessNoCoerce for ArrayWindows<'_, T, N> {
+    const MAY_HAVE_SIDE_EFFECT: bool = false;
+}
+
 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
 /// time), starting at the end of the slice.
 ///