Rollup of 10 pull requests

compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs

@@ -824,7 +824,7 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
                     }
                     ty => unreachable!("bswap {}", ty),
                 }
-            };
+            }
             let res = CValue::by_val(swap(&mut fx.bcx, arg), fx.layout_of(T));
             ret.write_cvalue(fx, res);
         };

compiler/rustc_error_codes/src/error_codes/E0373.md

@@ -50,3 +50,24 @@ fn foo() -> Box<Fn(u32) -> u32> {
 
 Now that the closure has its own copy of the data, there's no need to worry
 about safety.
+
+This error may also be encountered while using `async` blocks:
+
+```compile_fail,E0373,edition2018
+use std::future::Future;
+
+async fn f() {
+    let v = vec![1, 2, 3i32];
+    spawn(async { //~ ERROR E0373
+        println!("{:?}", v)
+    });
+}
+
+fn spawn<F: Future + Send + 'static>(future: F) {
+    unimplemented!()
+}
+```
+
+Similarly to closures, `async` blocks are not executed immediately and may
+capture closed-over data by reference. For more information, see
+https://rust-lang.github.io/async-book/03_async_await/01_chapter.html.

compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs

@@ -1318,21 +1318,30 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             Applicability::MachineApplicable,
         );
 
-        let msg = match category {
+        match category {
             ConstraintCategory::Return(_) | ConstraintCategory::OpaqueType => {
-                format!("{} is returned here", kind)
+                let msg = format!("{} is returned here", kind);
+                err.span_note(constraint_span, &msg);
             }
             ConstraintCategory::CallArgument => {
                 fr_name.highlight_region_name(&mut err);
-                format!("function requires argument type to outlive `{}`", fr_name)
+                if matches!(use_span.generator_kind(), Some(GeneratorKind::Async(_))) {
+                    err.note(
+                        "async blocks are not executed immediately and must either take a \
+                    reference or ownership of outside variables they use",
+                    );
+                } else {
+                    let msg = format!("function requires argument type to outlive `{}`", fr_name);
+                    err.span_note(constraint_span, &msg);
+                }
             }
             _ => bug!(
                 "report_escaping_closure_capture called with unexpected constraint \
                  category: `{:?}`",
                 category
             ),
-        };
-        err.span_note(constraint_span, &msg);
+        }
+
         err
     }
 

library/alloc/src/collections/binary_heap.rs

@@ -630,10 +630,16 @@ impl<T: Ord> BinaryHeap<T> {
         // and about 2 * (len1 + len2) comparisons in the worst case
         // while `extend` takes O(len2 * log(len1)) operations
         // and about 1 * len2 * log_2(len1) comparisons in the worst case,
-        // assuming len1 >= len2.
+        // assuming len1 >= len2. For larger heaps, the crossover point
+        // no longer follows this reasoning and was determined empirically.
         #[inline]
         fn better_to_rebuild(len1: usize, len2: usize) -> bool {
-            2 * (len1 + len2) < len2 * log2_fast(len1)
+            let tot_len = len1 + len2;
+            if tot_len <= 2048 {
+                2 * tot_len < len2 * log2_fast(len1)
+            } else {
+                2 * tot_len < len2 * 11
+            }
         }
 
         if better_to_rebuild(self.len(), other.len()) {

library/core/src/cell.rs

@@ -1261,6 +1261,40 @@ impl<'b, T: ?Sized> Ref<'b, T> {
         Ref { value: f(orig.value), borrow: orig.borrow }
     }
 
+    /// Makes a new `Ref` for an optional component of the borrowed data. The
+    /// original guard is returned as an `Err(..)` if the closure returns
+    /// `None`.
+    ///
+    /// The `RefCell` is already immutably borrowed, so this cannot fail.
+    ///
+    /// This is an associated function that needs to be used as
+    /// `Ref::filter_map(...)`. A method would interfere with methods of the same
+    /// name on the contents of a `RefCell` used through `Deref`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(cell_filter_map)]
+    ///
+    /// use std::cell::{RefCell, Ref};
+    ///
+    /// let c = RefCell::new(vec![1, 2, 3]);
+    /// let b1: Ref<Vec<u32>> = c.borrow();
+    /// let b2: Result<Ref<u32>, _> = Ref::filter_map(b1, |v| v.get(1));
+    /// assert_eq!(*b2.unwrap(), 2);
+    /// ```
+    #[unstable(feature = "cell_filter_map", reason = "recently added", issue = "81061")]
+    #[inline]
+    pub fn filter_map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Result<Ref<'b, U>, Self>
+    where
+        F: FnOnce(&T) -> Option<&U>,
+    {
+        match f(orig.value) {
+            Some(value) => Ok(Ref { value, borrow: orig.borrow }),
+            None => Err(orig),
+        }
+    }
+
     /// Splits a `Ref` into multiple `Ref`s for different components of the
     /// borrowed data.
     ///
@@ -1372,6 +1406,58 @@ impl<'b, T: ?Sized> RefMut<'b, T> {
         RefMut { value: f(value), borrow }
     }
 
+    /// Makes a new `RefMut` for an optional component of the borrowed data. The
+    /// original guard is returned as an `Err(..)` if the closure returns
+    /// `None`.
+    ///
+    /// The `RefCell` is already mutably borrowed, so this cannot fail.
+    ///
+    /// This is an associated function that needs to be used as
+    /// `RefMut::filter_map(...)`. A method would interfere with methods of the
+    /// same name on the contents of a `RefCell` used through `Deref`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(cell_filter_map)]
+    ///
+    /// use std::cell::{RefCell, RefMut};
+    ///
+    /// let c = RefCell::new(vec![1, 2, 3]);
+    ///
+    /// {
+    ///     let b1: RefMut<Vec<u32>> = c.borrow_mut();
+    ///     let mut b2: Result<RefMut<u32>, _> = RefMut::filter_map(b1, |v| v.get_mut(1));
+    ///
+    ///     if let Ok(mut b2) = b2 {
+    ///         *b2 += 2;
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(*c.borrow(), vec![1, 4, 3]);
+    /// ```
+    #[unstable(feature = "cell_filter_map", reason = "recently added", issue = "81061")]
+    #[inline]
+    pub fn filter_map<U: ?Sized, F>(orig: RefMut<'b, T>, f: F) -> Result<RefMut<'b, U>, Self>
+    where
+        F: FnOnce(&mut T) -> Option<&mut U>,
+    {
+        // FIXME(nll-rfc#40): fix borrow-check
+        let RefMut { value, borrow } = orig;
+        let value = value as *mut T;
+        // SAFETY: function holds onto an exclusive reference for the duration
+        // of its call through `orig`, and the pointer is only de-referenced
+        // inside of the function call never allowing the exclusive reference to
+        // escape.
+        match f(unsafe { &mut *value }) {
+            Some(value) => Ok(RefMut { value, borrow }),
+            None => {
+                // SAFETY: same as above.
+                Err(RefMut { value: unsafe { &mut *value }, borrow })
+            }
+        }
+    }
+
     /// Splits a `RefMut` into multiple `RefMut`s for different components of the
     /// borrowed data.
     ///

library/core/src/task/poll.rs

@@ -84,7 +84,7 @@ impl<T, E> Poll<Result<T, E>> {
 
 impl<T, E> Poll<Option<Result<T, E>>> {
     /// Changes the success value of this `Poll` with the closure provided.
-    #[unstable(feature = "poll_map", issue = "63514")]
+    #[stable(feature = "poll_map", since = "1.51.0")]
     pub fn map_ok<U, F>(self, f: F) -> Poll<Option<Result<U, E>>>
     where
         F: FnOnce(T) -> U,
@@ -98,7 +98,7 @@ impl<T, E> Poll<Option<Result<T, E>>> {
     }
 
     /// Changes the error value of this `Poll` with the closure provided.
-    #[unstable(feature = "poll_map", issue = "63514")]
+    #[stable(feature = "poll_map", since = "1.51.0")]
     pub fn map_err<U, F>(self, f: F) -> Poll<Option<Result<T, U>>>
     where
         F: FnOnce(E) -> U,

src/bootstrap/builder.rs

@@ -814,12 +814,22 @@ impl<'a> Builder<'a> {
             cargo.env("REAL_LIBRARY_PATH", e);
         }
 
+        // Found with `rg "init_env_logger\("`. If anyone uses `init_env_logger`
+        // from out of tree it shouldn't matter, since x.py is only used for
+        // building in-tree.
+        let color_logs = ["RUSTDOC_LOG_COLOR", "RUSTC_LOG_COLOR", "RUST_LOG_COLOR"];
         match self.build.config.color {
             Color::Always => {
                 cargo.arg("--color=always");
+                for log in &color_logs {
+                    cargo.env(log, "always");
+                }
             }
             Color::Never => {
                 cargo.arg("--color=never");
+                for log in &color_logs {
+                    cargo.env(log, "never");
+                }
             }
             Color::Auto => {} // nothing to do
         }