Rollup of 8 pull requests

compiler/rustc_feature/src/accepted.rs

@@ -285,6 +285,8 @@ declare_features! (
     (accepted, extended_key_value_attributes, "1.54.0", Some(78835), None),
     /// Allows unsizing coercions in `const fn`.
     (accepted, const_fn_unsize, "1.54.0", Some(64992), None),
+    /// Allows `impl Trait` with multiple unrelated lifetimes.
+    (accepted, member_constraints, "1.54.0", Some(61997), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: accepted features

compiler/rustc_feature/src/active.rs

@@ -472,9 +472,6 @@ declare_features! (
     /// Allows explicit discriminants on non-unit enum variants.
     (active, arbitrary_enum_discriminant, "1.37.0", Some(60553), None),
 
-    /// Allows `impl Trait` with multiple unrelated lifetimes.
-    (active, member_constraints, "1.37.0", Some(61997), None),
-
     /// Allows `async || body` closures.
     (active, async_closure, "1.37.0", Some(62290), None),
 

compiler/rustc_trait_selection/src/opaque_types.rs

@@ -140,15 +140,6 @@ pub trait InferCtxtExt<'tcx> {
         first_own_region_index: usize,
     );
 
-    /*private*/
-    fn member_constraint_feature_gate(
-        &self,
-        opaque_defn: &OpaqueTypeDecl<'tcx>,
-        opaque_type_def_id: DefId,
-        conflict1: ty::Region<'tcx>,
-        conflict2: ty::Region<'tcx>,
-    ) -> bool;
-
     fn infer_opaque_definition_from_instantiation(
         &self,
         def_id: DefId,
@@ -490,9 +481,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                         // ['a, 'b, 'c]`, where `'a..'c` are the
                         // regions that appear in the impl trait.
 
-                        // For now, enforce a feature gate outside of async functions.
-                        self.member_constraint_feature_gate(opaque_defn, def_id, lr, subst_region);
-
                         return self.generate_member_constraint(
                             concrete_ty,
                             opaque_defn,
@@ -559,60 +547,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         });
     }
 
-    /// Member constraints are presently feature-gated except for
-    /// async-await. We expect to lift this once we've had a bit more
-    /// time.
-    fn member_constraint_feature_gate(
-        &self,
-        opaque_defn: &OpaqueTypeDecl<'tcx>,
-        opaque_type_def_id: DefId,
-        conflict1: ty::Region<'tcx>,
-        conflict2: ty::Region<'tcx>,
-    ) -> bool {
-        // If we have `#![feature(member_constraints)]`, no problems.
-        if self.tcx.features().member_constraints {
-            return false;
-        }
-
-        let span = self.tcx.def_span(opaque_type_def_id);
-
-        // Without a feature-gate, we only generate member-constraints for async-await.
-        let context_name = match opaque_defn.origin {
-            // No feature-gate required for `async fn`.
-            hir::OpaqueTyOrigin::AsyncFn => return false,
-
-            // Otherwise, generate the label we'll use in the error message.
-            hir::OpaqueTyOrigin::Binding
-            | hir::OpaqueTyOrigin::FnReturn
-            | hir::OpaqueTyOrigin::TyAlias
-            | hir::OpaqueTyOrigin::Misc => "impl Trait",
-        };
-        let msg = format!("ambiguous lifetime bound in `{}`", context_name);
-        let mut err = self.tcx.sess.struct_span_err(span, &msg);
-
-        let conflict1_name = conflict1.to_string();
-        let conflict2_name = conflict2.to_string();
-        let label_owned;
-        let label = match (&*conflict1_name, &*conflict2_name) {
-            ("'_", "'_") => "the elided lifetimes here do not outlive one another",
-            _ => {
-                label_owned = format!(
-                    "neither `{}` nor `{}` outlives the other",
-                    conflict1_name, conflict2_name,
-                );
-                &label_owned
-            }
-        };
-        err.span_label(span, label);
-
-        if self.tcx.sess.is_nightly_build() {
-            err.help("add #![feature(member_constraints)] to the crate attributes to enable");
-        }
-
-        err.emit();
-        true
-    }
-
     /// Given the fully resolved, instantiated type for an opaque
     /// type, i.e., the value of an inference variable like C1 or C2
     /// (*), computes the "definition type" for an opaque type

library/alloc/src/rc.rs

@@ -1859,6 +1859,18 @@ where
     B: ToOwned + ?Sized,
     Rc<B>: From<&'a B> + From<B::Owned>,
 {
+    /// Create a reference-counted pointer from
+    /// a clone-on-write pointer by copying its content.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # use std::rc::Rc;
+    /// # use std::borrow::Cow;
+    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// let shared: Rc<str> = Rc::from(cow);
+    /// assert_eq!("eggplant", &shared[..]);
+    /// ```
     #[inline]
     fn from(cow: Cow<'a, B>) -> Rc<B> {
         match cow {
@@ -2303,7 +2315,7 @@ impl<T: ?Sized> Weak<T> {
 }
 
 #[stable(feature = "rc_weak", since = "1.4.0")]
-impl<T: ?Sized> Drop for Weak<T> {
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Weak<T> {
     /// Drops the `Weak` pointer.
     ///
     /// # Examples

library/alloc/src/sync.rs

@@ -2015,7 +2015,7 @@ impl<T> Default for Weak<T> {
 }
 
 #[stable(feature = "arc_weak", since = "1.4.0")]
-impl<T: ?Sized> Drop for Weak<T> {
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Weak<T> {
     /// Drops the `Weak` pointer.
     ///
     /// # Examples
@@ -2413,6 +2413,18 @@ where
     B: ToOwned + ?Sized,
     Arc<B>: From<&'a B> + From<B::Owned>,
 {
+    /// Create an atomically reference-counted pointer from
+    /// a clone-on-write pointer by copying its content.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # use std::sync::Arc;
+    /// # use std::borrow::Cow;
+    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// let shared: Arc<str> = Arc::from(cow);
+    /// assert_eq!("eggplant", &shared[..]);
+    /// ```
     #[inline]
     fn from(cow: Cow<'a, B>) -> Arc<B> {
         match cow {

library/alloc/tests/arc.rs

@@ -195,3 +195,18 @@ fn shared_from_iter_trustedlen_no_fuse() {
     assert_trusted_len(&iter);
     assert_eq!(&[Box::new(42), Box::new(24)], &*iter.collect::<Rc<[_]>>());
 }
+
+#[test]
+fn weak_may_dangle() {
+    fn hmm<'a>(val: &'a mut Weak<&'a str>) -> Weak<&'a str> {
+        val.clone()
+    }
+
+    // Without #[may_dangle] we get:
+    let mut val = Weak::new();
+    hmm(&mut val);
+    //  ~~~~~~~~ borrowed value does not live long enough
+    //
+    // `val` dropped here while still borrowed
+    // borrow might be used here, when `val` is dropped and runs the `Drop` code for type `std::sync::Weak`
+}

library/alloc/tests/rc.rs

@@ -191,3 +191,18 @@ fn shared_from_iter_trustedlen_no_fuse() {
     assert_trusted_len(&iter);
     assert_eq!(&[Box::new(42), Box::new(24)], &*iter.collect::<Rc<[_]>>());
 }
+
+#[test]
+fn weak_may_dangle() {
+    fn hmm<'a>(val: &'a mut Weak<&'a str>) -> Weak<&'a str> {
+        val.clone()
+    }
+
+    // Without #[may_dangle] we get:
+    let mut val = Weak::new();
+    hmm(&mut val);
+    //  ~~~~~~~~ borrowed value does not live long enough
+    //
+    // `val` dropped here while still borrowed
+    // borrow might be used here, when `val` is dropped and runs the `Drop` code for type `std::rc::Weak`
+}

library/core/src/ops/control_flow.rs

@@ -187,42 +187,41 @@ impl<B, C> ControlFlow<B, C> {
 #[cfg(bootstrap)]
 impl<R: ops::TryV1> ControlFlow<R, R::Output> {
     /// Create a `ControlFlow` from any type implementing `Try`.
-    #[unstable(feature = "control_flow_enum", reason = "new API", issue = "75744")]
     #[inline]
-    pub fn from_try(r: R) -> Self {
+    pub(crate) fn from_try(r: R) -> Self {
         match R::into_result(r) {
             Ok(v) => ControlFlow::Continue(v),
             Err(v) => ControlFlow::Break(R::from_error(v)),
         }
     }
 
     /// Convert a `ControlFlow` into any type implementing `Try`;
-    #[unstable(feature = "control_flow_enum", reason = "new API", issue = "75744")]
     #[inline]
-    pub fn into_try(self) -> R {
+    pub(crate) fn into_try(self) -> R {
         match self {
             ControlFlow::Continue(v) => R::from_ok(v),
             ControlFlow::Break(v) => v,
         }
     }
 }
 
+/// These are used only as part of implementing the iterator adapters.
+/// They have mediocre names and non-obvious semantics, so aren't
+/// currently on a path to potential stabilization.
 #[cfg(not(bootstrap))]
 impl<R: ops::TryV2> ControlFlow<R, R::Output> {
     /// Create a `ControlFlow` from any type implementing `Try`.
-    #[unstable(feature = "control_flow_enum", reason = "new API", issue = "75744")]
     #[inline]
-    pub fn from_try(r: R) -> Self {
+    pub(crate) fn from_try(r: R) -> Self {
         match R::branch(r) {
             ControlFlow::Continue(v) => ControlFlow::Continue(v),
             ControlFlow::Break(v) => ControlFlow::Break(R::from_residual(v)),
         }
     }
 
     /// Convert a `ControlFlow` into any type implementing `Try`;
-    #[unstable(feature = "control_flow_enum", reason = "new API", issue = "75744")]
     #[inline]
-    pub fn into_try(self) -> R {
+    pub(crate) fn into_try(self) -> R {
         match self {
             ControlFlow::Continue(v) => R::from_output(v),
             ControlFlow::Break(v) => v,

library/core/src/slice/mod.rs

@@ -3096,7 +3096,11 @@ impl<T> [T] {
         // SAFETY: the conditions for `ptr::copy` have all been checked above,
         // as have those for `ptr::add`.
         unsafe {
-            ptr::copy(self.as_ptr().add(src_start), self.as_mut_ptr().add(dest), count);
+            // Derive both `src_ptr` and `dest_ptr` from the same loan
+            let ptr = self.as_mut_ptr();
+            let src_ptr = ptr.add(src_start);
+            let dest_ptr = ptr.add(dest);
+            ptr::copy(src_ptr, dest_ptr, count);
         }
     }
 

library/std/src/sync/mutex.rs

@@ -294,8 +294,14 @@ impl<T: ?Sized> Mutex<T> {
     /// # Errors
     ///
     /// If another user of this mutex panicked while holding the mutex, then
-    /// this call will return an error if the mutex would otherwise be
-    /// acquired.
+    /// this call will return the [`Poisoned`] error if the mutex would
+    /// otherwise be acquired.
+    ///
+    /// If the mutex could not be acquired because it is already locked, then
+    /// this call will return the [`WouldBlock`] error.
+    ///
+    /// [`Poisoned`]: TryLockError::Poisoned
+    /// [`WouldBlock`]: TryLockError::WouldBlock
     ///
     /// # Examples
     ///

library/std/src/sync/rwlock.rs

@@ -199,11 +199,17 @@ impl<T: ?Sized> RwLock<T> {
     ///
     /// # Errors
     ///
-    /// This function will return an error if the RwLock is poisoned. An RwLock
-    /// is poisoned whenever a writer panics while holding an exclusive lock. An
-    /// error will only be returned if the lock would have otherwise been
+    /// This function will return the [`Poisoned`] error if the RwLock is poisoned.
+    /// An RwLock is poisoned whenever a writer panics while holding an exclusive
+    /// lock. `Poisoned` will only be returned if the lock would have otherwise been
     /// acquired.
     ///
+    /// This function will return the [`WouldBlock`] error if the RwLock could not
+    /// be acquired because it was already locked exclusively.
+    ///
+    /// [`Poisoned`]: TryLockError::Poisoned
+    /// [`WouldBlock`]: TryLockError::WouldBlock
+    ///
     /// # Examples
     ///
     /// ```
@@ -281,10 +287,17 @@ impl<T: ?Sized> RwLock<T> {
     ///
     /// # Errors
     ///
-    /// This function will return an error if the RwLock is poisoned. An RwLock
-    /// is poisoned whenever a writer panics while holding an exclusive lock. An
-    /// error will only be returned if the lock would have otherwise been
-    /// acquired.
+    /// This function will return the [`Poisoned`] error if the RwLock is
+    /// poisoned. An RwLock is poisoned whenever a writer panics while holding
+    /// an exclusive lock. `Poisoned` will only be returned if the lock would have
+    /// otherwise been acquired.
+    ///
+    /// This function will return the [`WouldBlock`] error if the RwLock could not
+    /// be acquired because it was already locked exclusively.
+    ///
+    /// [`Poisoned`]: TryLockError::Poisoned
+    /// [`WouldBlock`]: TryLockError::WouldBlock
+    ///
     ///
     /// # Examples
     ///

src/bootstrap/bootstrap.py

@@ -991,20 +991,28 @@ def update_submodules(self):
         ).decode(default_encoding).splitlines()]
         filtered_submodules = []
         submodules_names = []
+        llvm_checked_out = os.path.exists(os.path.join(self.rust_root, "src/llvm-project/.git"))
+        external_llvm_provided = self.get_toml('llvm-config') or self.downloading_llvm()
+        llvm_needed = not self.get_toml('codegen-backends', 'rust') \
+            or "llvm" in self.get_toml('codegen-backends', 'rust')
         for module in submodules:
-            # This is handled by native::Llvm in rustbuild, not here
             if module.endswith("llvm-project"):
-                continue
+                # Don't sync the llvm-project submodule if an external LLVM was
+                # provided, if we are downloading LLVM or if the LLVM backend is
+                # not being built. Also, if the submodule has been initialized
+                # already, sync it anyways so that it doesn't mess up contributor
+                # pull requests.
+                if external_llvm_provided or not llvm_needed:
+                    if self.get_toml('lld') != 'true' and not llvm_checked_out:
+                        continue
             check = self.check_submodule(module, slow_submodules)
             filtered_submodules.append((module, check))
             submodules_names.append(module)
         recorded = subprocess.Popen(["git", "ls-tree", "HEAD"] + submodules_names,
                                     cwd=self.rust_root, stdout=subprocess.PIPE)
         recorded = recorded.communicate()[0].decode(default_encoding).strip().splitlines()
-        # { filename: hash }
         recorded_submodules = {}
         for data in recorded:
-            # [mode, kind, hash, filename]
             data = data.split()
             recorded_submodules[data[3]] = data[2]
         for module in filtered_submodules:

src/bootstrap/lib.rs

@@ -472,22 +472,12 @@ impl Build {
         slice::from_ref(&self.build.triple)
     }
 
-    /// If the LLVM submodule has been initialized already, sync it unconditionally. This avoids
-    /// contributors checking in a submodule change by accident.
-    pub fn maybe_update_llvm_submodule(&self) {
-        if self.in_tree_llvm_info.is_git() {
-            native::update_llvm_submodule(self);
-        }
-    }
-
     /// Executes the entire build, as configured by the flags and configuration.
     pub fn build(&mut self) {
         unsafe {
             job::setup(self);
         }
 
-        self.maybe_update_llvm_submodule();
-
         if let Subcommand::Format { check, paths } = &self.config.cmd {
             return format::format(self, *check, &paths);
         }