Rollup of 7 pull requests

Cargo.lock

@@ -345,7 +345,6 @@ dependencies = [
  "libgit2-sys",
  "log",
  "memchr",
- "num_cpus",
  "opener",
  "openssl",
  "os_info",
@@ -1503,9 +1502,9 @@ dependencies = [
 
 [[package]]
 name = "git2"
-version = "0.13.23"
+version = "0.14.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2a8057932925d3a9d9e4434ea016570d37420ddb1ceed45a174d577f24ed6700"
+checksum = "6e7d3b96ec1fcaa8431cf04a4f1ef5caafe58d5cf7bcc31f09c1626adddb0ffe"
 dependencies = [
  "bitflags",
  "libc",
@@ -1518,9 +1517,9 @@ dependencies = [
 
 [[package]]
 name = "git2-curl"
-version = "0.14.1"
+version = "0.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "883539cb0ea94bab3f8371a98cd8e937bbe9ee7c044499184aa4c17deb643a50"
+checksum = "1ee51709364c341fbb6fe2a385a290fb9196753bdde2fc45447d27cd31b11b13"
 dependencies = [
  "curl",
  "git2",
@@ -1975,9 +1974,9 @@ dependencies = [
 
 [[package]]
 name = "libgit2-sys"
-version = "0.12.24+1.3.0"
+version = "0.13.1+1.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ddbd6021eef06fb289a8f54b3c2acfdd85ff2a585dfbb24b8576325373d2152c"
+checksum = "43e598aa7a4faedf1ea1b4608f582b06f0f40211eec551b7ef36019ae3f62def"
 dependencies = [
  "cc",
  "libc",

compiler/rustc_infer/src/infer/glb.rs

@@ -1,3 +1,5 @@
+//! Greatest lower bound. See [`lattice`].
+
 use super::combine::CombineFields;
 use super::lattice::{self, LatticeDir};
 use super::InferCtxt;

compiler/rustc_infer/src/infer/lattice.rs

@@ -1,23 +1,21 @@
-//! # Lattice Variables
+//! # Lattice variables
 //!
-//! This file contains generic code for operating on inference variables
-//! that are characterized by an upper- and lower-bound. The logic and
-//! reasoning is explained in detail in the large comment in `infer.rs`.
+//! Generic code for operating on [lattices] of inference variables
+//! that are characterized by an upper- and lower-bound.
 //!
-//! The code in here is defined quite generically so that it can be
+//! The code is defined quite generically so that it can be
 //! applied both to type variables, which represent types being inferred,
 //! and fn variables, which represent function types being inferred.
-//! It may eventually be applied to their types as well, who knows.
+//! (It may eventually be applied to their types as well.)
 //! In some cases, the functions are also generic with respect to the
 //! operation on the lattice (GLB vs LUB).
 //!
-//! Although all the functions are generic, we generally write the
-//! comments in a way that is specific to type variables and the LUB
-//! operation. It's just easier that way.
+//! ## Note
 //!
-//! In general all of the functions are defined parametrically
-//! over a `LatticeValue`, which is a value defined with respect to
-//! a lattice.
+//! Although all the functions are generic, for simplicity, comments in the source code
+//! generally refer to type variables and the LUB operation.
+//!
+//! [lattices]: https://en.wikipedia.org/wiki/Lattice_(order)
 
 use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use super::InferCtxt;
@@ -27,6 +25,11 @@ use rustc_middle::ty::relate::{RelateResult, TypeRelation};
 use rustc_middle::ty::TyVar;
 use rustc_middle::ty::{self, Ty};
 
+/// Trait for returning data about a lattice, and for abstracting
+/// over the "direction" of the lattice operation (LUB/GLB).
+///
+/// GLB moves "down" the lattice (to smaller values); LUB moves
+/// "up" the lattice (to bigger values).
 pub trait LatticeDir<'f, 'tcx>: TypeRelation<'tcx> {
     fn infcx(&self) -> &'f InferCtxt<'f, 'tcx>;
 
@@ -41,6 +44,7 @@ pub trait LatticeDir<'f, 'tcx>: TypeRelation<'tcx> {
     fn relate_bound(&mut self, v: Ty<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, ()>;
 }
 
+/// Relates two types using a given lattice.
 pub fn super_lattice_tys<'a, 'tcx: 'a, L>(
     this: &mut L,
     a: Ty<'tcx>,

compiler/rustc_infer/src/infer/lub.rs

@@ -1,3 +1,5 @@
+//! Least upper bound. See [`lattice`].
+
 use super::combine::CombineFields;
 use super::lattice::{self, LatticeDir};
 use super::InferCtxt;

compiler/rustc_middle/src/ty/sty.rs

@@ -1886,6 +1886,15 @@ impl<'tcx> Ty<'tcx> {
         }
     }
 
+    #[inline]
+    pub fn is_array_slice(self) -> bool {
+        match self.kind() {
+            Slice(_) => true,
+            RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_)),
+            _ => false,
+        }
+    }
+
     #[inline]
     pub fn is_array(self) -> bool {
         matches!(self.kind(), Array(..))

compiler/rustc_passes/src/check_attr.rs

@@ -1345,7 +1345,7 @@ impl CheckAttrVisitor<'_> {
         target: Target,
         item: Option<ItemLike<'_>>,
     ) -> bool {
-        let is_function = matches!(target, Target::Fn | Target::Method(..));
+        let is_function = matches!(target, Target::Fn);
         if !is_function {
             self.tcx
                 .sess

compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs

@@ -11,7 +11,7 @@ use std::iter;
 
 use super::InferCtxtPrivExt;
 
-crate trait InferCtxtExt<'tcx> {
+pub trait InferCtxtExt<'tcx> {
     /*private*/
     fn impl_similar_to(
         &self,
@@ -204,6 +204,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 flags.push((sym::_Self, Some("{integral}".to_owned())));
             }
 
+            if self_ty.is_array_slice() {
+                flags.push((sym::_Self, Some("&[]".to_owned())));
+            }
+
             if let ty::Array(aty, len) = self_ty.kind() {
                 flags.push((sym::_Self, Some("[]".to_owned())));
                 flags.push((sym::_Self, Some(format!("[{}]", aty))));