Rollup of 8 pull requests

compiler/rustc_data_structures/src/obligation_forest/mod.rs

@@ -426,6 +426,7 @@ impl<O: ForestObligation> ObligationForest<O> {
             // nodes. Therefore we use a `while` loop.
             let mut index = 0;
             while let Some(node) = self.nodes.get_mut(index) {
+                // This test is extremely hot.
                 if node.state.get() != NodeState::Pending
                     || !processor.needs_process_obligation(&node.obligation)
                 {
@@ -439,6 +440,7 @@ impl<O: ForestObligation> ObligationForest<O> {
                 // out of sync with `nodes`. It's not very common, but it does
                 // happen, and code in `compress` has to allow for it.
 
+                // This code is much less hot.
                 match processor.process_obligation(&mut node.obligation) {
                     ProcessResult::Unchanged => {
                         // No change in state.

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -36,7 +36,6 @@ use rustc_trait_selection::traits::{self, ObligationCauseCode, SelectionContext}
 
 use std::iter;
 use std::mem;
-use std::slice;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(in super::super) fn check_casts(&mut self) {
@@ -1507,11 +1506,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let coerce = if blk.targeted_by_break {
             CoerceMany::new(coerce_to_ty)
         } else {
-            let tail_expr: &[&hir::Expr<'_>] = match tail_expr {
-                Some(e) => slice::from_ref(e),
-                None => &[],
-            };
-            CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
+            CoerceMany::with_coercion_sites(coerce_to_ty, blk.expr.as_slice())
         };
 
         let prev_diverges = self.diverges.get();

compiler/rustc_hir_typeck/src/lib.rs

@@ -5,6 +5,7 @@
 #![feature(min_specialization)]
 #![feature(control_flow_enum)]
 #![feature(drain_filter)]
+#![feature(option_as_slice)]
 #![allow(rustc::potential_query_instability)]
 #![recursion_limit = "256"]
 

compiler/rustc_hir_typeck/src/op.rs

@@ -749,14 +749,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         let opname = Ident::with_dummy_span(opname);
-        let input_types =
-            opt_rhs.as_ref().map(|(_, ty)| std::slice::from_ref(ty)).unwrap_or_default();
+        let (opt_rhs_expr, opt_rhs_ty) = opt_rhs.unzip();
+        let input_types = opt_rhs_ty.as_slice();
         let cause = self.cause(
             span,
             traits::BinOp {
-                rhs_span: opt_rhs.map(|(expr, _)| expr.span),
-                is_lit: opt_rhs
-                    .map_or(false, |(expr, _)| matches!(expr.kind, hir::ExprKind::Lit(_))),
+                rhs_span: opt_rhs_expr.map(|expr| expr.span),
+                is_lit: opt_rhs_expr
+                    .map_or(false, |expr| matches!(expr.kind, hir::ExprKind::Lit(_))),
                 output_ty: expected.only_has_type(self),
             },
         );

compiler/rustc_hir_typeck/src/place_op.rs

@@ -11,7 +11,6 @@ use rustc_middle::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutabili
 use rustc_middle::ty::{self, Ty};
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
-use std::slice;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// Type-check `*oprnd_expr` with `oprnd_expr` type-checked already.
@@ -393,11 +392,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 Some(self.typeck_results.borrow().node_substs(expr.hir_id).type_at(1))
             }
         };
-        let arg_tys = match arg_ty {
-            None => &[],
-            Some(ref ty) => slice::from_ref(ty),
-        };
-
+        let arg_tys = arg_ty.as_slice();
         let method = self.try_mutable_overloaded_place_op(expr.span, base_ty, arg_tys, op);
         let method = match method {
             Some(ok) => self.register_infer_ok_obligations(ok),

compiler/rustc_infer/locales/en-US.ftl

@@ -345,3 +345,6 @@ infer_prlf_defined_without_sub = the lifetime defined here...
 infer_prlf_must_oultive_with_sup = ...must outlive the lifetime `{$sup_symbol}` defined here
 infer_prlf_must_oultive_without_sup = ...must outlive the lifetime defined here
 infer_prlf_known_limitation = this is a known limitation that will be removed in the future (see issue #100013 <https://github.com/rust-lang/rust/issues/100013> for more information)
+
+infer_opaque_captures_lifetime = hidden type for `{$opaque_ty}` captures lifetime that does not appear in bounds
+    .label = opaque type defined here

compiler/rustc_infer/src/errors/mod.rs

@@ -1147,3 +1147,13 @@ pub enum PlaceholderRelationLfNotSatisfied {
         note: (),
     },
 }
+
+#[derive(Diagnostic)]
+#[diag(infer_opaque_captures_lifetime, code = "E0700")]
+pub struct OpaqueCapturesLifetime<'tcx> {
+    #[primary_span]
+    pub span: Span,
+    #[label]
+    pub opaque_ty_span: Span,
+    pub opaque_ty: Ty<'tcx>,
+}

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -49,6 +49,7 @@ use super::lexical_region_resolve::RegionResolutionError;
 use super::region_constraints::GenericKind;
 use super::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TypeTrace, ValuePairs};
 
+use crate::errors;
 use crate::infer;
 use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
 use crate::infer::ExpectedFound;
@@ -281,15 +282,13 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
     span: Span,
     hidden_ty: Ty<'tcx>,
     hidden_region: ty::Region<'tcx>,
-    opaque_ty: ty::OpaqueTypeKey<'tcx>,
+    opaque_ty_key: ty::OpaqueTypeKey<'tcx>,
 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-    let opaque_ty = tcx.mk_opaque(opaque_ty.def_id.to_def_id(), opaque_ty.substs);
-    let mut err = struct_span_err!(
-        tcx.sess,
+    let mut err = tcx.sess.create_err(errors::OpaqueCapturesLifetime {
         span,
-        E0700,
-        "hidden type for `{opaque_ty}` captures lifetime that does not appear in bounds",
-    );
+        opaque_ty: tcx.mk_opaque(opaque_ty_key.def_id.to_def_id(), opaque_ty_key.substs),
+        opaque_ty_span: tcx.def_span(opaque_ty_key.def_id),
+    });
 
     // Explain the region we are capturing.
     match *hidden_region {

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -212,36 +212,44 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
 
     /// Identifies whether a predicate obligation needs processing.
     ///
-    /// This is always inlined, despite its size, because it has a single
-    /// callsite and it is called *very* frequently.
+    /// This is always inlined because it has a single callsite and it is
+    /// called *very* frequently. Be careful modifying this code! Several
+    /// compile-time benchmarks are very sensitive to even small changes.
     #[inline(always)]
     fn needs_process_obligation(&self, pending_obligation: &Self::Obligation) -> bool {
         // If we were stalled on some unresolved variables, first check whether
         // any of them have been resolved; if not, don't bother doing more work
         // yet.
-        match pending_obligation.stalled_on.len() {
-            // Match arms are in order of frequency, which matters because this
-            // code is so hot. 1 and 0 dominate; 2+ is fairly rare.
-            1 => {
-                let infer_var = pending_obligation.stalled_on[0];
-                self.selcx.infcx.ty_or_const_infer_var_changed(infer_var)
-            }
-            0 => {
-                // In this case we haven't changed, but wish to make a change.
-                true
-            }
-            _ => {
-                // This `for` loop was once a call to `all()`, but this lower-level
-                // form was a perf win. See #64545 for details.
-                (|| {
-                    for &infer_var in &pending_obligation.stalled_on {
-                        if self.selcx.infcx.ty_or_const_infer_var_changed(infer_var) {
-                            return true;
-                        }
+        let stalled_on = &pending_obligation.stalled_on;
+        match stalled_on.len() {
+            // This case is the hottest most of the time, being hit up to 99%
+            // of the time. `keccak` and `cranelift-codegen-0.82.1` are
+            // benchmarks that particularly stress this path.
+            1 => self.selcx.infcx.ty_or_const_infer_var_changed(stalled_on[0]),
+
+            // In this case we haven't changed, but wish to make a change. Note
+            // that this is a special case, and is not equivalent to the `_`
+            // case below, which would return `false` for an empty `stalled_on`
+            // vector.
+            //
+            // This case is usually hit only 1% of the time or less, though it
+            // reaches 20% in `wasmparser-0.101.0`.
+            0 => true,
+
+            // This case is usually hit only 1% of the time or less, though it
+            // reaches 95% in `mime-0.3.16`, 64% in `wast-54.0.0`, and 12% in
+            // `inflate-0.4.5`.
+            //
+            // The obvious way of writing this, with a call to `any()` and no
+            // closure, is currently slower than this version.
+            _ => (|| {
+                for &infer_var in stalled_on {
+                    if self.selcx.infcx.ty_or_const_infer_var_changed(infer_var) {
+                        return true;
                     }
-                    false
-                })()
-            }
+                }
+                false
+            })(),
         }
     }
 

library/alloc/src/rc.rs

@@ -2145,7 +2145,7 @@ impl<T, I: iter::TrustedLen<Item = T>> ToRcSlice<T> for I {
                 Rc::from_iter_exact(self, low)
             }
         } else {
-            // TrustedLen contract guarantees that `upper_bound == `None` implies an iterator
+            // TrustedLen contract guarantees that `upper_bound == None` implies an iterator
             // length exceeding `usize::MAX`.
             // The default implementation would collect into a vec which would panic.
             // Thus we panic here immediately without invoking `Vec` code.

library/alloc/src/sync.rs

@@ -2895,7 +2895,7 @@ impl<T, I: iter::TrustedLen<Item = T>> ToArcSlice<T> for I {
                 Arc::from_iter_exact(self, low)
             }
         } else {
-            // TrustedLen contract guarantees that `upper_bound == `None` implies an iterator
+            // TrustedLen contract guarantees that `upper_bound == None` implies an iterator
             // length exceeding `usize::MAX`.
             // The default implementation would collect into a vec which would panic.
             // Thus we panic here immediately without invoking `Vec` code.

library/core/src/any.rs

@@ -56,7 +56,7 @@
 //!     let value_any = value as &dyn Any;
 //!
 //!     // Try to convert our value to a `String`. If successful, we want to
-//!     // output the String`'s length as well as its value. If not, it's a
+//!     // output the `String`'s length as well as its value. If not, it's a
 //!     // different type: just print it out unadorned.
 //!     match value_any.downcast_ref::<String>() {
 //!         Some(as_string) => {

library/core/src/cell.rs

@@ -632,7 +632,7 @@ pub struct RefCell<T: ?Sized> {
     // Stores the location of the earliest currently active borrow.
     // This gets updated whenever we go from having zero borrows
     // to having a single borrow. When a borrow occurs, this gets included
-    // in the generated `BorrowError/`BorrowMutError`
+    // in the generated `BorrowError`/`BorrowMutError`
     #[cfg(feature = "debug_refcell")]
     borrowed_at: Cell<Option<&'static crate::panic::Location<'static>>>,
     value: UnsafeCell<T>,

library/core/src/intrinsics/mir.rs

@@ -42,7 +42,7 @@
 //! another function. The `dialect` and `phase` parameters indicate which [version of MIR][dialect
 //! docs] you are inserting here. Generally you'll want to use `#![custom_mir(dialect = "built")]`
 //! if you want your MIR to be modified by the full MIR pipeline, or `#![custom_mir(dialect =
-//! "runtime", phase = "optimized")] if you don't.
+//! "runtime", phase = "optimized")]` if you don't.
 //!
 //! [dialect docs]:
 //!     https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/mir/enum.MirPhase.html

library/core/src/ptr/alignment.rs

@@ -41,7 +41,7 @@ impl Alignment {
     /// Returns the alignment for a type.
     ///
     /// This provides the same numerical value as [`mem::align_of`],
-    /// but in an `Alignment` instead of a `usize.
+    /// but in an `Alignment` instead of a `usize`.
     #[unstable(feature = "ptr_alignment_type", issue = "102070")]
     #[inline]
     pub const fn of<T>() -> Self {

library/core/src/slice/mod.rs

@@ -2955,7 +2955,7 @@ impl<T> [T] {
         // This operation is still `O(n)`.
         //
         // Example: We start in this state, where `r` represents "next
-        // read" and `w` represents "next_write`.
+        // read" and `w` represents "next_write".
         //
         //           r
         //     +---+---+---+---+---+---+

library/core/src/slice/sort.rs

@@ -317,7 +317,7 @@ where
     // 1. `block` - Number of elements in the block.
     // 2. `start` - Start pointer into the `offsets` array.
     // 3. `end` - End pointer into the `offsets` array.
-    // 4. `offsets - Indices of out-of-order elements within the block.
+    // 4. `offsets` - Indices of out-of-order elements within the block.
 
     // The current block on the left side (from `l` to `l.add(block_l)`).
     let mut l = v.as_mut_ptr();
@@ -327,7 +327,7 @@ where
     let mut offsets_l = [MaybeUninit::<u8>::uninit(); BLOCK];
 
     // The current block on the right side (from `r.sub(block_r)` to `r`).
-    // SAFETY: The documentation for .add() specifically mention that `vec.as_ptr().add(vec.len())` is always safe`
+    // SAFETY: The documentation for .add() specifically mention that `vec.as_ptr().add(vec.len())` is always safe
     let mut r = unsafe { l.add(v.len()) };
     let mut block_r = BLOCK;
     let mut start_r = ptr::null_mut();