Rollup of 6 pull requests

src/bootstrap/bin/rustc.rs

@@ -316,6 +316,11 @@ fn main() {
         }
     }
 
+    // This is required for internal lints.
+    if stage != "0" {
+        cmd.arg("-Zunstable-options");
+    }
+
     // Force all crates compiled by this compiler to (a) be unstable and (b)
     // allow the `rustc_private` feature to link to other unstable crates
     // also in the sysroot. We also do this for host crates, since those

src/doc/man/rustc.1

@@ -265,8 +265,8 @@ Optimize with possible levels 0\[en]3
 
 .SH ENVIRONMENT
 
-Some of these affect the output of the compiler, while others affect programs
-which link to the standard library.
+Some of these affect only test harness programs (generated via rustc --test);
+others affect all programs which link to the Rust standard library.
 
 .TP
 \fBRUST_TEST_THREADS\fR

src/libarena/lib.rs

@@ -12,6 +12,7 @@
        test(no_crate_inject, attr(deny(warnings))))]
 
 #![deny(rust_2018_idioms)]
+#![cfg_attr(not(stage0), deny(internal))]
 
 #![feature(alloc)]
 #![feature(core_intrinsics)]

src/libcore/borrow.rs

@@ -32,6 +32,10 @@
 /// on the identical behavior of these additional trait implementations.
 /// These traits will likely appear as additional trait bounds.
 ///
+/// In particular `Eq`, `Ord` and `Hash` must be equivalent for
+/// borrowed and owned values: `x.borrow() == y.borrow()` should give the
+/// same result as `x == y`.
+///
 /// If generic code merely needs to work for all types that can
 /// provide a reference to related type `T`, it is often better to use
 /// [`AsRef<T>`] as more types can safely implement it.

src/libcore/convert.rs

@@ -105,11 +105,13 @@ pub const fn identity<T>(x: T) -> T { x }
 /// `&T` or write a custom function.
 ///
 ///
-/// `AsRef` is very similar to, but serves a slightly different purpose than [`Borrow`]:
+/// `AsRef` has the same signature as [`Borrow`], but `Borrow` is different in few aspects:
 ///
-/// - Use `AsRef` when the goal is to simply convert into a reference
-/// - Use `Borrow` when the goal is related to writing code that is agnostic to
-///   the type of borrow and whether it is a reference or value
+/// - Unlike `AsRef`, `Borrow` has a blanket impl for any `T`, and can be used to accept either
+///   a reference or a value.
+/// - `Borrow` also requires that `Hash`, `Eq` and `Ord` for borrowed value are
+///   equivalent to those of the owned value. For this reason, if you want to
+///   borrow only a single field of a struct you can implement `AsRef`, but not `Borrow`.
 ///
 /// [`Borrow`]: ../../std/borrow/trait.Borrow.html
 ///

src/libcore/hint.rs

@@ -50,15 +50,28 @@ pub unsafe fn unreachable_unchecked() -> ! {
     intrinsics::unreachable()
 }
 
-/// Save power or switch hyperthreads in a busy-wait spin-loop.
+/// Signals the processor that it is entering a busy-wait spin-loop.
 ///
-/// This function is deliberately more primitive than
-/// [`std::thread::yield_now`](../../std/thread/fn.yield_now.html) and
-/// does not directly yield to the system's scheduler.
-/// In some cases it might be useful to use a combination of both functions.
-/// Careful benchmarking is advised.
+/// Upon receiving spin-loop signal the processor can optimize its behavior by, for example, saving
+/// power or switching hyper-threads.
 ///
-/// On some platforms this function may not do anything at all.
+/// This function is different than [`std::thread::yield_now`] which directly yields to the
+/// system's scheduler, whereas `spin_loop` only signals the processor that it is entering a
+/// busy-wait spin-loop without yielding control to the system's scheduler.
+///
+/// Using a busy-wait spin-loop with `spin_loop` is ideally used in situations where a
+/// contended lock is held by another thread executed on a different CPU and where the waiting
+/// times are relatively small. Because entering busy-wait spin-loop does not trigger the system's
+/// scheduler, no overhead for switching threads occurs. However, if the thread holding the
+/// contended lock is running on the same CPU, the spin-loop is likely to occupy an entire CPU slice
+/// before switching to the thread that holds the lock. If the contending lock is held by a thread
+/// on the same CPU or if the waiting times for acquiring the lock are longer, it is often better to
+/// use [`std::thread::yield_now`].
+///
+/// **Note**: On platforms that do not support receiving spin-loop hints this function does not
+/// do anything at all.
+///
+/// [`std::thread::yield_now`]: ../../std/thread/fn.yield_now.html
 #[inline]
 #[unstable(feature = "renamed_spin_loop", issue = "55002")]
 pub fn spin_loop() {

src/libcore/sync/atomic.rs

@@ -124,15 +124,28 @@ use fmt;
 
 use hint::spin_loop;
 
-/// Save power or switch hyperthreads in a busy-wait spin-loop.
+/// Signals the processor that it is entering a busy-wait spin-loop.
 ///
-/// This function is deliberately more primitive than
-/// [`std::thread::yield_now`](../../../std/thread/fn.yield_now.html) and
-/// does not directly yield to the system's scheduler.
-/// In some cases it might be useful to use a combination of both functions.
-/// Careful benchmarking is advised.
+/// Upon receiving spin-loop signal the processor can optimize its behavior by, for example, saving
+/// power or switching hyper-threads.
 ///
-/// On some platforms this function may not do anything at all.
+/// This function is different than [`std::thread::yield_now`] which directly yields to the
+/// system's scheduler, whereas `spin_loop_hint` only signals the processor that it is entering a
+/// busy-wait spin-loop without yielding control to the system's scheduler.
+///
+/// Using a busy-wait spin-loop with `spin_loop_hint` is ideally used in situations where a
+/// contended lock is held by another thread executed on a different CPU and where the waiting
+/// times are relatively small. Because entering busy-wait spin-loop does not trigger the system's
+/// scheduler, no overhead for switching threads occurs. However, if the thread holding the
+/// contended lock is running on the same CPU, the spin-loop is likely to occupy an entire CPU slice
+/// before switching to the thread that holds the lock. If the contending lock is held by a thread
+/// on the same CPU or if the waiting times for acquiring the lock are longer, it is often better to
+/// use [`std::thread::yield_now`].
+///
+/// **Note**: On platforms that do not support receiving spin-loop hints this function does not
+/// do anything at all.
+///
+/// [`std::thread::yield_now`]: ../../../std/thread/fn.yield_now.html
 #[inline]
 #[stable(feature = "spin_loop_hint", since = "1.24.0")]
 pub fn spin_loop_hint() {

src/libfmt_macros/lib.rs

@@ -9,6 +9,7 @@
        test(attr(deny(warnings))))]
 
 #![deny(rust_2018_idioms)]
+#![cfg_attr(not(stage0), deny(internal))]
 
 #![feature(nll)]
 #![feature(rustc_private)]

src/librustc/hir/def_id.rs

@@ -1,10 +1,10 @@
-use crate::ty;
-use crate::ty::TyCtxt;
-use crate::hir::map::definitions::FIRST_FREE_HIGH_DEF_INDEX;
+use crate::ty::{self, print::Printer, subst::Kind, Ty, TyCtxt};
+use crate::hir::map::definitions::{DisambiguatedDefPathData, FIRST_FREE_HIGH_DEF_INDEX};
 use rustc_data_structures::indexed_vec::Idx;
 use serialize;
 use std::fmt;
 use std::u32;
+use syntax::symbol::{LocalInternedString, Symbol};
 
 newtype_index! {
     pub struct CrateId {
@@ -252,6 +252,107 @@ impl DefId {
             format!("module `{}`", tcx.def_path_str(*self))
         }
     }
+
+    /// Check if a `DefId`'s path matches the given absolute type path usage.
+    // Uplifted from rust-lang/rust-clippy
+    pub fn match_path<'a, 'tcx>(self, tcx: TyCtxt<'a, 'tcx, 'tcx>, path: &[&str]) -> bool {
+        pub struct AbsolutePathPrinter<'a, 'tcx> {
+            pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
+        }
+
+        impl<'tcx> Printer<'tcx, 'tcx> for AbsolutePathPrinter<'_, 'tcx> {
+            type Error = !;
+
+            type Path = Vec<LocalInternedString>;
+            type Region = ();
+            type Type = ();
+            type DynExistential = ();
+
+            fn tcx<'a>(&'a self) -> TyCtxt<'a, 'tcx, 'tcx> {
+                self.tcx
+            }
+
+            fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
+                Ok(())
+            }
+
+            fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
+                Ok(())
+            }
+
+            fn print_dyn_existential(
+                self,
+                _predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
+                ) -> Result<Self::DynExistential, Self::Error> {
+                Ok(())
+            }
+
+            fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
+                Ok(vec![self.tcx.original_crate_name(cnum).as_str()])
+            }
+
+            fn path_qualified(
+                self,
+                self_ty: Ty<'tcx>,
+                trait_ref: Option<ty::TraitRef<'tcx>>,
+                ) -> Result<Self::Path, Self::Error> {
+                if trait_ref.is_none() {
+                    if let ty::Adt(def, substs) = self_ty.sty {
+                        return self.print_def_path(def.did, substs);
+                    }
+                }
+
+                // This shouldn't ever be needed, but just in case:
+                Ok(vec![match trait_ref {
+                    Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)).as_str(),
+                    None => Symbol::intern(&format!("<{}>", self_ty)).as_str(),
+                }])
+            }
+
+            fn path_append_impl(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                _disambiguated_data: &DisambiguatedDefPathData,
+                self_ty: Ty<'tcx>,
+                trait_ref: Option<ty::TraitRef<'tcx>>,
+                ) -> Result<Self::Path, Self::Error> {
+                let mut path = print_prefix(self)?;
+
+                // This shouldn't ever be needed, but just in case:
+                path.push(match trait_ref {
+                    Some(trait_ref) => {
+                        Symbol::intern(&format!("<impl {} for {}>", trait_ref, self_ty)).as_str()
+                    },
+                    None => Symbol::intern(&format!("<impl {}>", self_ty)).as_str(),
+                });
+
+                Ok(path)
+            }
+
+            fn path_append(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                disambiguated_data: &DisambiguatedDefPathData,
+                ) -> Result<Self::Path, Self::Error> {
+                let mut path = print_prefix(self)?;
+                path.push(disambiguated_data.data.as_interned_str().as_str());
+                Ok(path)
+            }
+
+            fn path_generic_args(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                _args: &[Kind<'tcx>],
+                ) -> Result<Self::Path, Self::Error> {
+                print_prefix(self)
+            }
+        }
+
+        let names = AbsolutePathPrinter { tcx }.print_def_path(self, &[]).unwrap();
+
+        names.len() == path.len()
+            && names.into_iter().zip(path.iter()).all(|(a, &b)| *a == *b)
+    }
 }
 
 impl serialize::UseSpecializedEncodable for DefId {}

src/librustc/ich/hcx.rs

@@ -9,7 +9,6 @@ use crate::session::Session;
 
 use std::cmp::Ord;
 use std::hash as std_hash;
-use std::collections::HashMap;
 use std::cell::RefCell;
 
 use syntax::ast;
@@ -394,13 +393,12 @@ impl<'a> HashStable<StableHashingContext<'a>> for DelimSpan {
     }
 }
 
-pub fn hash_stable_trait_impls<'a, 'gcx, W, R>(
+pub fn hash_stable_trait_impls<'a, 'gcx, W>(
     hcx: &mut StableHashingContext<'a>,
     hasher: &mut StableHasher<W>,
     blanket_impls: &[DefId],
-    non_blanket_impls: &HashMap<fast_reject::SimplifiedType, Vec<DefId>, R>)
-    where W: StableHasherResult,
-          R: std_hash::BuildHasher,
+    non_blanket_impls: &FxHashMap<fast_reject::SimplifiedType, Vec<DefId>>)
+    where W: StableHasherResult
 {
     {
         let mut blanket_impls: SmallVec<[_; 8]> = blanket_impls

src/librustc/infer/error_reporting/mod.rs

@@ -56,7 +56,7 @@ use crate::hir::Node;
 use crate::middle::region;
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use crate::ty::error::TypeError;
-use crate::ty::{self, subst::{Subst, SubstsRef}, Region, Ty, TyCtxt, TyKind, TypeFoldable};
+use crate::ty::{self, subst::{Subst, SubstsRef}, Region, Ty, TyCtxt, TypeFoldable};
 use errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
 use std::{cmp, fmt};
 use syntax_pos::{Pos, Span};
@@ -1094,14 +1094,14 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 (_, false, _) => {
                     if let Some(exp_found) = exp_found {
                         let (def_id, ret_ty) = match exp_found.found.sty {
-                            TyKind::FnDef(def, _) => {
+                            ty::FnDef(def, _) => {
                                 (Some(def), Some(self.tcx.fn_sig(def).output()))
                             }
                             _ => (None, None),
                         };
 
                         let exp_is_struct = match exp_found.expected.sty {
-                            TyKind::Adt(def, _) => def.is_struct(),
+                            ty::Adt(def, _) => def.is_struct(),
                             _ => false,
                         };
 
@@ -1140,8 +1140,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         diag: &mut DiagnosticBuilder<'tcx>,
     ) {
         match (&exp_found.expected.sty, &exp_found.found.sty) {
-            (TyKind::Adt(exp_def, exp_substs), TyKind::Ref(_, found_ty, _)) => {
-                if let TyKind::Adt(found_def, found_substs) = found_ty.sty {
+            (ty::Adt(exp_def, exp_substs), ty::Ref(_, found_ty, _)) => {
+                if let ty::Adt(found_def, found_substs) = found_ty.sty {
                     let path_str = format!("{:?}", exp_def);
                     if exp_def == &found_def {
                         let opt_msg = "you can convert from `&Option<T>` to `Option<&T>` using \
@@ -1164,17 +1164,17 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                             let mut show_suggestion = true;
                             for (exp_ty, found_ty) in exp_substs.types().zip(found_substs.types()) {
                                 match exp_ty.sty {
-                                    TyKind::Ref(_, exp_ty, _) => {
+                                    ty::Ref(_, exp_ty, _) => {
                                         match (&exp_ty.sty, &found_ty.sty) {
-                                            (_, TyKind::Param(_)) |
-                                            (_, TyKind::Infer(_)) |
-                                            (TyKind::Param(_), _) |
-                                            (TyKind::Infer(_), _) => {}
+                                            (_, ty::Param(_)) |
+                                            (_, ty::Infer(_)) |
+                                            (ty::Param(_), _) |
+                                            (ty::Infer(_), _) => {}
                                             _ if ty::TyS::same_type(exp_ty, found_ty) => {}
                                             _ => show_suggestion = false,
                                         };
                                     }
-                                    TyKind::Param(_) | TyKind::Infer(_) => {}
+                                    ty::Param(_) | ty::Infer(_) => {}
                                     _ => show_suggestion = false,
                                 }
                             }

src/librustc/lib.rs

@@ -29,6 +29,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 
 #![deny(rust_2018_idioms)]
+#![cfg_attr(not(stage0), deny(internal))]
 #![allow(explicit_outlives_requirements)]
 
 #![feature(arbitrary_self_types)]