Rollup of 5 pull requests

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -2135,22 +2135,20 @@ impl<'a> State<'a> {
             ast::ExprKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, true),
             ast::ExprKind::Break(opt_label, ref opt_expr) => {
                 self.word("break");
-                self.space();
                 if let Some(label) = opt_label {
-                    self.print_ident(label.ident);
                     self.space();
+                    self.print_ident(label.ident);
                 }
                 if let Some(ref expr) = *opt_expr {
-                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                     self.space();
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                 }
             }
             ast::ExprKind::Continue(opt_label) => {
                 self.word("continue");
-                self.space();
                 if let Some(label) = opt_label {
+                    self.space();
                     self.print_ident(label.ident);
-                    self.space()
                 }
             }
             ast::ExprKind::Ret(ref result) => {

compiler/rustc_hir_pretty/src/lib.rs

@@ -1543,22 +1543,20 @@ impl<'a> State<'a> {
             hir::ExprKind::Path(ref qpath) => self.print_qpath(qpath, true),
             hir::ExprKind::Break(destination, ref opt_expr) => {
                 self.word("break");
-                self.space();
                 if let Some(label) = destination.label {
-                    self.print_ident(label.ident);
                     self.space();
+                    self.print_ident(label.ident);
                 }
                 if let Some(ref expr) = *opt_expr {
-                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                     self.space();
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                 }
             }
             hir::ExprKind::Continue(destination) => {
                 self.word("continue");
-                self.space();
                 if let Some(label) = destination.label {
+                    self.space();
                     self.print_ident(label.ident);
-                    self.space()
                 }
             }
             hir::ExprKind::Ret(ref result) => {

compiler/rustc_interface/src/passes.rs

@@ -10,7 +10,7 @@ use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::parallel;
 use rustc_data_structures::sync::{Lrc, OnceCell, WorkerLocal};
 use rustc_data_structures::temp_dir::MaybeTempDir;
-use rustc_errors::{ErrorReported, PResult};
+use rustc_errors::{Applicability, ErrorReported, PResult};
 use rustc_expand::base::ExtCtxt;
 use rustc_hir::def_id::{StableCrateId, LOCAL_CRATE};
 use rustc_hir::Crate;
@@ -456,10 +456,26 @@ pub fn configure_and_expand(
         identifiers.sort_by_key(|&(key, _)| key);
         for (ident, mut spans) in identifiers.into_iter() {
             spans.sort();
-            sess.diagnostic().span_err(
-                MultiSpan::from(spans),
-                &format!("identifiers cannot contain emoji: `{}`", ident),
-            );
+            if ident == sym::ferris {
+                let first_span = spans[0];
+                sess.diagnostic()
+                    .struct_span_err(
+                        MultiSpan::from(spans),
+                        "Ferris cannot be used as an identifier",
+                    )
+                    .span_suggestion(
+                        first_span,
+                        "try using their name instead",
+                        "ferris".to_string(),
+                        Applicability::MaybeIncorrect,
+                    )
+                    .emit();
+            } else {
+                sess.diagnostic().span_err(
+                    MultiSpan::from(spans),
+                    &format!("identifiers cannot contain emoji: `{}`", ident),
+                );
+            }
         }
     });
 

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -329,9 +329,7 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
     fn mir_to_initial_sorted_coverage_spans(&self) -> Vec<CoverageSpan> {
         let mut initial_spans = Vec::<CoverageSpan>::with_capacity(self.mir_body.num_nodes() * 2);
         for (bcb, bcb_data) in self.basic_coverage_blocks.iter_enumerated() {
-            for coverage_span in self.bcb_to_initial_coverage_spans(bcb, bcb_data) {
-                initial_spans.push(coverage_span);
-            }
+            initial_spans.extend(self.bcb_to_initial_coverage_spans(bcb, bcb_data));
         }
 
         if initial_spans.is_empty() {

compiler/rustc_span/src/symbol.rs

@@ -630,6 +630,7 @@ symbols! {
         fdiv_fast,
         feature,
         fence,
+        ferris: "🦀",
         fetch_update,
         ffi,
         ffi_const,

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -498,9 +498,7 @@ fn orphan_check_trait_ref<'tcx>(
             return Err(OrphanCheckErr::UncoveredTy(input_ty, local_type));
         }
 
-        for input_ty in non_local_tys {
-            non_local_spans.push((input_ty, i == 0));
-        }
+        non_local_spans.extend(non_local_tys.into_iter().map(|input_ty| (input_ty, i == 0)));
     }
     // If we exit above loop, never found a local type.
     debug!("orphan_check_trait_ref: no local type");

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -362,9 +362,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .infcx
             .probe(|_| self.match_projection_obligation_against_definition_bounds(obligation));
 
-        for predicate_index in result {
-            candidates.vec.push(ProjectionCandidate(predicate_index));
-        }
+        candidates.vec.extend(result.into_iter().map(ProjectionCandidate));
     }
 
     /// Given an obligation like `<SomeTrait for T>`, searches the obligations that the caller

compiler/rustc_typeck/src/check/mod.rs

@@ -686,9 +686,8 @@ fn bounds_from_generic_predicates<'tcx>(
     };
     let mut where_clauses = vec![];
     for (ty, bounds) in types {
-        for bound in &bounds {
-            where_clauses.push(format!("{}: {}", ty, tcx.def_path_str(*bound)));
-        }
+        where_clauses
+            .extend(bounds.into_iter().map(|bound| format!("{}: {}", ty, tcx.def_path_str(bound))));
     }
     for projection in &projections {
         let p = projection.skip_binder();

compiler/rustc_typeck/src/check/upvar.rs

@@ -904,10 +904,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> MigrationWarningReason {
         let mut reasons = MigrationWarningReason::default();
 
-        for auto_trait in auto_trait_reasons {
-            reasons.auto_traits.push(auto_trait);
-        }
-
+        reasons.auto_traits.extend(auto_trait_reasons);
         reasons.drop_order = drop_order;
 
         reasons

library/core/src/future/join.rs

@@ -0,0 +1,147 @@
+#![allow(unused_imports)] // items are used by the macro
+
+use crate::cell::UnsafeCell;
+use crate::future::{poll_fn, Future};
+use crate::mem;
+use crate::pin::Pin;
+use crate::task::{Context, Poll};
+
+/// Polls multiple futures simultaneously, returning a tuple
+/// of all results once complete.
+///
+/// While `join!(a, b)` is similar to `(a.await, b.await)`,
+/// `join!` polls both futures concurrently and is therefore more efficient.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(future_join, future_poll_fn)]
+///
+/// use std::future::join;
+///
+/// async fn one() -> usize { 1 }
+/// async fn two() -> usize { 2 }
+///
+/// # let _ =  async {
+/// let x = join!(one(), two()).await;
+/// assert_eq!(x, (1, 2));
+/// # };
+/// ```
+///
+/// `join!` is variadic, so you can pass any number of futures:
+///
+/// ```
+/// #![feature(future_join, future_poll_fn)]
+///
+/// use std::future::join;
+///
+/// async fn one() -> usize { 1 }
+/// async fn two() -> usize { 2 }
+/// async fn three() -> usize { 3 }
+///
+/// # let _ = async {
+/// let x = join!(one(), two(), three()).await;
+/// assert_eq!(x, (1, 2, 3));
+/// # };
+/// ```
+#[unstable(feature = "future_join", issue = "91642")]
+pub macro join {
+    ( $($fut:expr),* $(,)?) => {
+        join! { @count: (), @futures: {}, @rest: ($($fut,)*) }
+    },
+    // Recurse until we have the position of each future in the tuple
+    (
+        // A token for each future that has been expanded: "_ _ _"
+        @count: ($($count:tt)*),
+        // Futures and their positions in the tuple: "{ a => (_), b => (_ _)) }"
+        @futures: { $($fut:tt)* },
+        // Take a future from @rest to expand
+        @rest: ($current:expr, $($rest:tt)*)
+    ) => {
+        join! {
+            @count: ($($count)* _),
+            @futures: { $($fut)* $current => ($($count)*), },
+            @rest: ($($rest)*)
+        }
+    },
+    // Now generate the output future
+    (
+        @count: ($($count:tt)*),
+        @futures: {
+            $( $(@$f:tt)? $fut:expr => ( $($pos:tt)* ), )*
+        },
+        @rest: ()
+    ) => {
+        async move {
+            let mut futures = ( $( MaybeDone::Future($fut), )* );
+
+            poll_fn(move |cx| {
+                let mut done = true;
+
+                $(
+                    let ( $($pos,)* fut, .. ) = &mut futures;
+
+                    // SAFETY: The futures are never moved
+                    done &= unsafe { Pin::new_unchecked(fut).poll(cx).is_ready() };
+                )*
+
+                if done {
+                    // Extract all the outputs
+                    Poll::Ready(($({
+                        let ( $($pos,)* fut, .. ) = &mut futures;
+
+                        fut.take_output().unwrap()
+                    }),*))
+                } else {
+                    Poll::Pending
+                }
+            }).await
+        }
+    }
+}
+
+/// Future used by `join!` that stores it's output to
+/// be later taken and doesn't panic when polled after ready.
+///
+/// This type is public in a private module for use by the macro.
+#[allow(missing_debug_implementations)]
+#[unstable(feature = "future_join", issue = "91642")]
+pub enum MaybeDone<F: Future> {
+    Future(F),
+    Done(F::Output),
+    Took,
+}
+
+#[unstable(feature = "future_join", issue = "91642")]
+impl<F: Future> MaybeDone<F> {
+    pub fn take_output(&mut self) -> Option<F::Output> {
+        match &*self {
+            MaybeDone::Done(_) => match mem::replace(self, Self::Took) {
+                MaybeDone::Done(val) => Some(val),
+                _ => unreachable!(),
+            },
+            _ => None,
+        }
+    }
+}
+
+#[unstable(feature = "future_join", issue = "91642")]
+impl<F: Future> Future for MaybeDone<F> {
+    type Output = ();
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        // SAFETY: pinning in structural for `f`
+        unsafe {
+            match self.as_mut().get_unchecked_mut() {
+                MaybeDone::Future(f) => match Pin::new_unchecked(f).poll(cx) {
+                    Poll::Ready(val) => self.set(Self::Done(val)),
+                    Poll::Pending => return Poll::Pending,
+                },
+                MaybeDone::Done(_) => {}
+                MaybeDone::Took => unreachable!(),
+            }
+        }
+
+        Poll::Ready(())
+    }
+}

library/core/src/future/mod.rs

@@ -11,13 +11,17 @@ use crate::{
 
 mod future;
 mod into_future;
+mod join;
 mod pending;
 mod poll_fn;
 mod ready;
 
 #[stable(feature = "futures_api", since = "1.36.0")]
 pub use self::future::Future;
 
+#[unstable(feature = "future_join", issue = "91642")]
+pub use self::join::join;
+
 #[unstable(feature = "into_future", issue = "67644")]
 pub use into_future::IntoFuture;