Rollup of 7 pull requests

src/liballoc/sync.rs

@@ -867,12 +867,10 @@ impl<T: ?Sized> Arc<T> {
     unsafe fn drop_slow(&mut self) {
         // Destroy the data at this time, even though we may not free the box
         // allocation itself (there may still be weak pointers lying around).
-        ptr::drop_in_place(&mut self.ptr.as_mut().data);
+        ptr::drop_in_place(Self::get_mut_unchecked(self));
 
-        if self.inner().weak.fetch_sub(1, Release) == 1 {
-            acquire!(self.inner().weak);
-            Global.dealloc(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()))
-        }
+        // Drop the weak ref collectively held by all strong references
+        drop(Weak { ptr: self.ptr });
     }
 
     #[inline]
@@ -1204,7 +1202,7 @@ impl<T: Clone> Arc<T> {
 
         // As with `get_mut()`, the unsafety is ok because our reference was
         // either unique to begin with, or became one upon cloning the contents.
-        unsafe { &mut this.ptr.as_mut().data }
+        unsafe { Self::get_mut_unchecked(this) }
     }
 }
 
@@ -1280,7 +1278,9 @@ impl<T: ?Sized> Arc<T> {
     #[inline]
     #[unstable(feature = "get_mut_unchecked", issue = "63292")]
     pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T {
-        &mut this.ptr.as_mut().data
+        // We are careful to *not* create a reference covering the "count" fields, as
+        // this would alias with concurrent access to the reference counts (e.g. by `Weak`).
+        &mut (*this.ptr.as_ptr()).data
     }
 
     /// Determine whether this is the unique reference (including weak refs) to
@@ -1571,6 +1571,13 @@ impl<T> Weak<T> {
     }
 }
 
+/// Helper type to allow accessing the reference counts without
+/// making any assertions about the data field.
+struct WeakInner<'a> {
+    weak: &'a atomic::AtomicUsize,
+    strong: &'a atomic::AtomicUsize,
+}
+
 impl<T: ?Sized> Weak<T> {
     /// Attempts to upgrade the `Weak` pointer to an [`Arc`], delaying
     /// dropping of the inner value if successful.
@@ -1678,8 +1685,18 @@ impl<T: ?Sized> Weak<T> {
     /// Returns `None` when the pointer is dangling and there is no allocated `ArcInner`,
     /// (i.e., when this `Weak` was created by `Weak::new`).
     #[inline]
-    fn inner(&self) -> Option<&ArcInner<T>> {
-        if is_dangling(self.ptr) { None } else { Some(unsafe { self.ptr.as_ref() }) }
+    fn inner(&self) -> Option<WeakInner<'_>> {
+        if is_dangling(self.ptr) {
+            None
+        } else {
+            // We are careful to *not* create a reference covering the "data" field, as
+            // the field may be mutated concurrently (for example, if the last `Arc`
+            // is dropped, the data field will be dropped in-place).
+            Some(unsafe {
+                let ptr = self.ptr.as_ptr();
+                WeakInner { strong: &(*ptr).strong, weak: &(*ptr).weak }
+            })
+        }
     }
 
     /// Returns `true` if the two `Weak`s point to the same allocation (similar to

src/libcore/cell.rs

@@ -849,11 +849,11 @@ impl<T: ?Sized> RefCell<T> {
     /// ```
     /// use std::cell::RefCell;
     ///
-    /// let c = RefCell::new(5);
+    /// let c = RefCell::new("hello".to_owned());
     ///
-    /// *c.borrow_mut() = 7;
+    /// *c.borrow_mut() = "bonjour".to_owned();
     ///
-    /// assert_eq!(*c.borrow(), 7);
+    /// assert_eq!(&*c.borrow(), "bonjour");
     /// ```
     ///
     /// An example of panic:

src/libcore/iter/traits/double_ended.rs

@@ -63,6 +63,32 @@ pub trait DoubleEndedIterator: Iterator {
     /// assert_eq!(None, iter.next());
     /// assert_eq!(None, iter.next_back());
     /// ```
+    ///
+    /// # Remarks
+    ///
+    /// The elements yielded by `DoubleEndedIterator`'s methods may differ from
+    /// the ones yielded by `Iterator`'s methods:
+    ///
+    /// ```
+    /// let vec = vec![(1, 'a'), (1, 'b'), (1, 'c'), (2, 'a'), (2, 'b')];
+    /// let uniq_by_fst_comp = || {
+    ///     let mut seen = std::collections::HashSet::new();
+    ///     vec.iter().copied().filter(move |x| seen.insert(x.0))
+    /// };
+    ///
+    /// assert_eq!(uniq_by_fst_comp().last(), Some((2, 'a')));
+    /// assert_eq!(uniq_by_fst_comp().next_back(), Some((2, 'b')));
+    ///
+    /// assert_eq!(
+    ///     uniq_by_fst_comp().fold(vec![], |mut v, x| {v.push(x); v}),
+    ///     vec![(1, 'a'), (2, 'a')]
+    /// );
+    /// assert_eq!(
+    ///     uniq_by_fst_comp().rfold(vec![], |mut v, x| {v.push(x); v}),
+    ///     vec![(2, 'b'), (1, 'c')]
+    /// );
+    /// ```
+    ///
     #[stable(feature = "rust1", since = "1.0.0")]
     fn next_back(&mut self) -> Option<Self::Item>;
 

src/librustc_middle/ty/sty.rs

@@ -764,8 +764,8 @@ impl<'tcx> TraitRef<'tcx> {
 pub type PolyTraitRef<'tcx> = Binder<TraitRef<'tcx>>;
 
 impl<'tcx> PolyTraitRef<'tcx> {
-    pub fn self_ty(&self) -> Ty<'tcx> {
-        self.skip_binder().self_ty()
+    pub fn self_ty(&self) -> Binder<Ty<'tcx>> {
+        self.map_bound_ref(|tr| tr.self_ty())
     }
 
     pub fn def_id(&self) -> DefId {

src/librustc_parse/parser/diagnostics.rs

@@ -935,6 +935,19 @@ impl<'a> Parser<'a> {
             return self.expect(&token::Semi).map(drop);
         } else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) {
             // The current token is in the same line as the prior token, not recoverable.
+        } else if [token::Comma, token::Colon].contains(&self.token.kind)
+            && &self.prev_token.kind == &token::CloseDelim(token::Paren)
+        {
+            // Likely typo: The current token is on a new line and is expected to be
+            // `.`, `;`, `?`, or an operator after a close delimiter token.
+            //
+            // let a = std::process::Command::new("echo")
+            //         .arg("1")
+            //         ,arg("2")
+            //         ^
+            // https://github.com/rust-lang/rust/issues/72253
+            self.expect(&token::Semi)?;
+            return Ok(());
         } else if self.look_ahead(1, |t| {
             t == &token::CloseDelim(token::Brace) || t.can_begin_expr() && t.kind != token::Colon
         }) && [token::Comma, token::Colon].contains(&self.token.kind)

src/librustc_trait_selection/traits/error_reporting/mod.rs

@@ -289,7 +289,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                             (
                                 Some(format!(
                                     "`?` couldn't convert the error to `{}`",
-                                    trait_ref.self_ty(),
+                                    trait_ref.skip_binder().self_ty(),
                                 )),
                                 Some(
                                     "the question mark operation (`?`) implicitly performs a \
@@ -339,7 +339,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                             if let Some(ret_span) = self.return_type_span(obligation) {
                                 err.span_label(
                                     ret_span,
-                                    &format!("expected `{}` because of this", trait_ref.self_ty()),
+                                    &format!(
+                                        "expected `{}` because of this",
+                                        trait_ref.skip_binder().self_ty()
+                                    ),
                                 );
                             }
                         }
@@ -352,7 +355,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                                     "{}the trait `{}` is not implemented for `{}`",
                                     pre_message,
                                     trait_ref.print_only_trait_path(),
-                                    trait_ref.self_ty(),
+                                    trait_ref.skip_binder().self_ty(),
                                 )
                             };
 
@@ -642,7 +645,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     return;
                 }
 
-                let found_trait_ty = found_trait_ref.self_ty();
+                let found_trait_ty = match found_trait_ref.self_ty().no_bound_vars() {
+                    Some(ty) => ty,
+                    None => return,
+                };
 
                 let found_did = match found_trait_ty.kind {
                     ty::Closure(did, _) | ty::Foreign(did) | ty::FnDef(did, _) => Some(did),
@@ -1359,11 +1365,15 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
     ) {
         let get_trait_impl = |trait_def_id| {
             let mut trait_impl = None;
-            self.tcx.for_each_relevant_impl(trait_def_id, trait_ref.self_ty(), |impl_def_id| {
-                if trait_impl.is_none() {
-                    trait_impl = Some(impl_def_id);
-                }
-            });
+            self.tcx.for_each_relevant_impl(
+                trait_def_id,
+                trait_ref.skip_binder().self_ty(),
+                |impl_def_id| {
+                    if trait_impl.is_none() {
+                        trait_impl = Some(impl_def_id);
+                    }
+                },
+            );
             trait_impl
         };
         let required_trait_path = self.tcx.def_path_str(trait_ref.def_id());
@@ -1434,7 +1444,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
         let mut err = match predicate.kind() {
             ty::PredicateKind::Trait(ref data, _) => {
                 let trait_ref = data.to_poly_trait_ref();
-                let self_ty = trait_ref.self_ty();
+                let self_ty = trait_ref.skip_binder().self_ty();
                 debug!("self_ty {:?} {:?} trait_ref {:?}", self_ty, self_ty.kind, trait_ref);
 
                 if predicate.references_error() {
@@ -1552,7 +1562,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
             }
             ty::PredicateKind::Projection(ref data) => {
                 let trait_ref = data.to_poly_trait_ref(self.tcx);
-                let self_ty = trait_ref.self_ty();
+                let self_ty = trait_ref.skip_binder().self_ty();
                 let ty = data.skip_binder().ty;
                 if predicate.references_error() {
                     return;

src/librustc_trait_selection/traits/error_reporting/suggestions.rs

@@ -318,7 +318,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         trait_ref: ty::PolyTraitRef<'tcx>,
         body_id: hir::HirId,
     ) {
-        let self_ty = trait_ref.self_ty();
+        let self_ty = trait_ref.skip_binder().self_ty();
         let (param_ty, projection) = match &self_ty.kind {
             ty::Param(_) => (true, None),
             ty::Projection(projection) => (false, Some(projection)),
@@ -524,7 +524,11 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         trait_ref: &ty::Binder<ty::TraitRef<'tcx>>,
         points_at_arg: bool,
     ) {
-        let self_ty = trait_ref.self_ty();
+        let self_ty = match trait_ref.self_ty().no_bound_vars() {
+            None => return,
+            Some(ty) => ty,
+        };
+
         let (def_id, output_ty, callable) = match self_ty.kind {
             ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig().output(), "closure"),
             ty::FnDef(def_id, _) => (def_id, self_ty.fn_sig(self.tcx).output(), "function"),
@@ -829,6 +833,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         span: Span,
         trait_ref: &ty::Binder<ty::TraitRef<'tcx>>,
     ) {
+        let is_empty_tuple =
+            |ty: ty::Binder<Ty<'_>>| ty.skip_binder().kind == ty::Tuple(ty::List::empty());
+
         let hir = self.tcx.hir();
         let parent_node = hir.get_parent_node(obligation.cause.body_id);
         let node = hir.find(parent_node);
@@ -840,7 +847,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             if let hir::ExprKind::Block(blk, _) = &body.value.kind {
                 if sig.decl.output.span().overlaps(span)
                     && blk.expr.is_none()
-                    && "()" == &trait_ref.self_ty().to_string()
+                    && is_empty_tuple(trait_ref.self_ty())
                 {
                     // FIXME(estebank): When encountering a method with a trait
                     // bound not satisfied in the return type with a body that has
@@ -1271,7 +1278,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 ObligationCauseCode::DerivedObligation(derived_obligation)
                 | ObligationCauseCode::BuiltinDerivedObligation(derived_obligation)
                 | ObligationCauseCode::ImplDerivedObligation(derived_obligation) => {
-                    let ty = derived_obligation.parent_trait_ref.self_ty();
+                    let ty = derived_obligation.parent_trait_ref.skip_binder().self_ty();
                     debug!(
                         "maybe_note_obligation_cause_for_async_await: \
                             parent_trait_ref={:?} self_ty.kind={:?}",
@@ -1911,7 +1918,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
                 let impls_future = self.tcx.type_implements_trait((
                     future_trait,
-                    self_ty,
+                    self_ty.skip_binder(),
                     ty::List::empty(),
                     obligation.param_env,
                 ));
@@ -1927,7 +1934,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 let projection_ty = ty::ProjectionTy {
                     // `T`
                     substs: self.tcx.mk_substs_trait(
-                        trait_ref.self_ty(),
+                        trait_ref.self_ty().skip_binder(),
                         self.fresh_substs_for_item(span, item_def_id),
                     ),
                     // `Future::Output`

src/librustc_trait_selection/traits/select.rs

@@ -1040,17 +1040,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         &mut self,
         stack: &TraitObligationStack<'o, 'tcx>,
     ) -> SelectionResult<'tcx, SelectionCandidate<'tcx>> {
-        if stack.obligation.predicate.references_error() {
-            // If we encounter a `Error`, we generally prefer the
-            // most "optimistic" result in response -- that is, the
-            // one least likely to report downstream errors. But
-            // because this routine is shared by coherence and by
-            // trait selection, there isn't an obvious "right" choice
-            // here in that respect, so we opt to just return
-            // ambiguity and let the upstream clients sort it out.
-            return Ok(None);
-        }
-
         if let Some(conflict) = self.is_knowable(stack) {
             debug!("coherence stage: not knowable");
             if self.intercrate_ambiguity_causes.is_some() {

src/librustc_trait_selection/traits/specialize/mod.rs

@@ -496,7 +496,7 @@ fn to_pretty_impl_header(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Option<String>
     for (p, _) in predicates {
         if let Some(poly_trait_ref) = p.to_opt_poly_trait_ref() {
             if Some(poly_trait_ref.def_id()) == sized_trait {
-                types_without_default_bounds.remove(poly_trait_ref.self_ty());
+                types_without_default_bounds.remove(poly_trait_ref.self_ty().skip_binder());
                 continue;
             }
         }

src/librustc_typeck/check/mod.rs

@@ -3810,7 +3810,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         trait_ref: ty::PolyTraitRef<'tcx>,
         expected_vid: ty::TyVid,
     ) -> bool {
-        let self_ty = self.shallow_resolve(trait_ref.self_ty());
+        let self_ty = self.shallow_resolve(trait_ref.skip_binder().self_ty());
         debug!(
             "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
             trait_ref, self_ty, expected_vid

src/librustdoc/clean/mod.rs

@@ -500,7 +500,7 @@ impl<'a> Clean<WherePredicate> for ty::PolyTraitPredicate<'a> {
     fn clean(&self, cx: &DocContext<'_>) -> WherePredicate {
         let poly_trait_ref = self.map_bound(|pred| pred.trait_ref);
         WherePredicate::BoundPredicate {
-            ty: poly_trait_ref.self_ty().clean(cx),
+            ty: poly_trait_ref.skip_binder().self_ty().clean(cx),
             bounds: vec![poly_trait_ref.clean(cx)],
         }
     }
@@ -755,7 +755,7 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics, ty::GenericPredicates<'tcx
                 let mut projection = None;
                 let param_idx = (|| {
                     if let Some(trait_ref) = p.to_opt_poly_trait_ref() {
-                        if let ty::Param(param) = trait_ref.self_ty().kind {
+                        if let ty::Param(param) = trait_ref.skip_binder().self_ty().kind {
                             return Some(param.index);
                         }
                     } else if let Some(outlives) = p.to_opt_type_outlives() {

src/test/ui/async-await/issue-72590-type-error-sized.rs

@@ -0,0 +1,22 @@
+// Regression test for issue #72590
+// Tests that we don't emit a spurious "size cannot be statically determined" error
+// edition:2018
+
+struct Foo {
+    foo: Nonexistent, //~ ERROR cannot find
+    other: str
+}
+
+struct Bar {
+    test: Missing //~ ERROR cannot find
+}
+
+impl Foo {
+    async fn frob(self) {} //~ ERROR the size
+}
+
+impl Bar {
+    async fn myfn(self) {}
+}
+
+fn main() {}