Auto merge of rust-lang#70747 - Centril:rollup-2vx9bve, r=Centril

Rollup of 9 pull requests

Successful merges:

 - rust-lang#69860 (Use associated numeric consts in documentation)
 - rust-lang#70576 (Update the description of the ticket to point at RFC 1721)
 - rust-lang#70597 (Fix double-free and undefined behaviour in libstd::syn::unix::Thread::new)
 - rust-lang#70640 (Hide `task_context` when lowering body)
 - rust-lang#70641 (Remove duplicated code in trait selection)
 - rust-lang#70707 (Remove unused graphviz emitter)
 - rust-lang#70720 (Place TLS initializers with relocations in .tdata)
 - rust-lang#70735 (Clean up E0502 explanation)
 - rust-lang#70741 (Add test for rust-lang#59023)

Failed merges:

r? @ghost

Author: bors

Diff for: src/liballoc/slice.rs

@@ -432,7 +432,7 @@ impl<T> [T] {
     ///
     /// ```should_panic
     /// // this will panic at runtime
-    /// b"0123456789abcdef".repeat(usize::max_value());
+    /// b"0123456789abcdef".repeat(usize::MAX);
     /// ```
     #[stable(feature = "repeat_generic_slice", since = "1.40.0")]
     pub fn repeat(&self, n: usize) -> Vec<T>

Diff for: src/liballoc/str.rs

@@ -499,7 +499,7 @@ impl str {
     ///
     /// ```should_panic
     /// // this will panic at runtime
-    /// "0123456789abcdef".repeat(usize::max_value());
+    /// "0123456789abcdef".repeat(usize::MAX);
     /// ```
     #[stable(feature = "repeat_str", since = "1.16.0")]
     pub fn repeat(&self, n: usize) -> String {

Diff for: src/libcore/cmp.rs

@@ -817,7 +817,7 @@ pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> {
     /// When comparison is impossible:
     ///
     /// ```
-    /// let result = std::f64::NAN.partial_cmp(&1.0);
+    /// let result = f64::NAN.partial_cmp(&1.0);
     /// assert_eq!(result, None);
     /// ```
     #[must_use]

Diff for: src/libcore/fmt/mod.rs

@@ -852,7 +852,7 @@ pub trait LowerHex {
 ///     }
 /// }
 ///
-/// let l = Length(i32::max_value());
+/// let l = Length(i32::MAX);
 ///
 /// assert_eq!(format!("l as hex is: {:X}", l), "l as hex is: 7FFFFFFF");
 ///

Diff for: src/libcore/hint.rs

@@ -43,7 +43,7 @@ use crate::intrinsics;
 ///
 /// assert_eq!(div_1(7, 0), 7);
 /// assert_eq!(div_1(9, 1), 4);
-/// assert_eq!(div_1(11, std::u32::MAX), 0);
+/// assert_eq!(div_1(11, u32::MAX), 0);
 /// ```
 #[inline]
 #[stable(feature = "unreachable", since = "1.27.0")]

Diff for: src/libcore/intrinsics.rs

@@ -1739,19 +1739,19 @@ extern "rust-intrinsic" {
     pub fn mul_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
 
     /// Performs an exact division, resulting in undefined behavior where
-    /// `x % y != 0` or `y == 0` or `x == T::min_value() && y == -1`
+    /// `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`
     pub fn exact_div<T: Copy>(x: T, y: T) -> T;
 
     /// Performs an unchecked division, resulting in undefined behavior
-    /// where y = 0 or x = `T::min_value()` and y = -1
+    /// where y = 0 or x = `T::MIN` and y = -1
     ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `checked_div` method. For example,
     /// [`std::u32::checked_div`](../../std/primitive.u32.html#method.checked_div)
     #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
     pub fn unchecked_div<T: Copy>(x: T, y: T) -> T;
     /// Returns the remainder of an unchecked division, resulting in
-    /// undefined behavior where y = 0 or x = `T::min_value()` and y = -1
+    /// undefined behavior where y = 0 or x = `T::MIN` and y = -1
     ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `checked_rem` method. For example,
@@ -1777,17 +1777,17 @@ extern "rust-intrinsic" {
     pub fn unchecked_shr<T: Copy>(x: T, y: T) -> T;
 
     /// Returns the result of an unchecked addition, resulting in
-    /// undefined behavior when `x + y > T::max_value()` or `x + y < T::min_value()`.
+    /// undefined behavior when `x + y > T::MAX` or `x + y < T::MIN`.
     #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
     pub fn unchecked_add<T: Copy>(x: T, y: T) -> T;
 
     /// Returns the result of an unchecked subtraction, resulting in
-    /// undefined behavior when `x - y > T::max_value()` or `x - y < T::min_value()`.
+    /// undefined behavior when `x - y > T::MAX` or `x - y < T::MIN`.
     #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
     pub fn unchecked_sub<T: Copy>(x: T, y: T) -> T;
 
     /// Returns the result of an unchecked multiplication, resulting in
-    /// undefined behavior when `x * y > T::max_value()` or `x * y < T::min_value()`.
+    /// undefined behavior when `x * y > T::MAX` or `x * y < T::MIN`.
     #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
     pub fn unchecked_mul<T: Copy>(x: T, y: T) -> T;
 

Diff for: src/libcore/iter/traits/iterator.rs

@@ -198,7 +198,7 @@ pub trait Iterator {
     /// // and the maximum possible lower bound
     /// let iter = 0..;
     ///
-    /// assert_eq!((usize::max_value(), None), iter.size_hint());
+    /// assert_eq!((usize::MAX, None), iter.size_hint());
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -2920,7 +2920,7 @@ pub trait Iterator {
     /// assert_eq!([1.].iter().partial_cmp([1., 2.].iter()), Some(Ordering::Less));
     /// assert_eq!([1., 2.].iter().partial_cmp([1.].iter()), Some(Ordering::Greater));
     ///
-    /// assert_eq!([std::f64::NAN].iter().partial_cmp([1.].iter()), None);
+    /// assert_eq!([f64::NAN].iter().partial_cmp([1.].iter()), None);
     /// ```
     #[stable(feature = "iter_order", since = "1.5.0")]
     fn partial_cmp<I>(self, other: I) -> Option<Ordering>
@@ -3170,7 +3170,7 @@ pub trait Iterator {
     /// assert!(![1, 3, 2, 4].iter().is_sorted());
     /// assert!([0].iter().is_sorted());
     /// assert!(std::iter::empty::<i32>().is_sorted());
-    /// assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
+    /// assert!(![0.0, 1.0, f32::NAN].iter().is_sorted());
     /// ```
     #[inline]
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
@@ -3197,7 +3197,7 @@ pub trait Iterator {
     /// assert!(![1, 3, 2, 4].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
     /// assert!([0].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
     /// assert!(std::iter::empty::<i32>().is_sorted_by(|a, b| a.partial_cmp(b)));
-    /// assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
+    /// assert!(![0.0, 1.0, f32::NAN].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
     /// ```
     ///
     /// [`is_sorted`]: trait.Iterator.html#method.is_sorted

Diff for: src/libcore/num/f32.rs

@@ -470,7 +470,7 @@ impl f32 {
     ///
     /// let value = -128.9_f32;
     /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
-    /// assert_eq!(rounded, std::i8::MIN);
+    /// assert_eq!(rounded, i8::MIN);
     /// ```
     ///
     /// # Safety

Diff for: src/libcore/num/f64.rs

@@ -484,7 +484,7 @@ impl f64 {
     ///
     /// let value = -128.9_f32;
     /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
-    /// assert_eq!(rounded, std::i8::MIN);
+    /// assert_eq!(rounded, i8::MIN);
     /// ```
     ///
     /// # Safety

Diff for: src/libcore/num/mod.rs

@@ -174,7 +174,7 @@ NonZeroI8 NonZeroI16 NonZeroI32 NonZeroI64 NonZeroI128 NonZeroIsize }
 /// let zero = Wrapping(0u32);
 /// let one = Wrapping(1u32);
 ///
-/// assert_eq!(std::u32::MAX, (zero - one).0);
+/// assert_eq!(u32::MAX, (zero - one).0);
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default, Hash)]

Diff for: src/libcore/ops/range.rs

@@ -139,10 +139,9 @@ impl<Idx: PartialOrd<Idx>> Range<Idx> {
     /// ```
     /// #![feature(range_is_empty)]
     ///
-    /// use std::f32::NAN;
     /// assert!(!(3.0..5.0).is_empty());
-    /// assert!( (3.0..NAN).is_empty());
-    /// assert!( (NAN..5.0).is_empty());
+    /// assert!( (3.0..f32::NAN).is_empty());
+    /// assert!( (f32::NAN..5.0).is_empty());
     /// ```
     #[unstable(feature = "range_is_empty", reason = "recently added", issue = "48111")]
     pub fn is_empty(&self) -> bool {
@@ -496,10 +495,9 @@ impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
     /// ```
     /// #![feature(range_is_empty)]
     ///
-    /// use std::f32::NAN;
     /// assert!(!(3.0..=5.0).is_empty());
-    /// assert!( (3.0..=NAN).is_empty());
-    /// assert!( (NAN..=5.0).is_empty());
+    /// assert!( (3.0..=f32::NAN).is_empty());
+    /// assert!( (f32::NAN..=5.0).is_empty());
     /// ```
     ///
     /// This method returns `true` after iteration has finished:

Diff for: src/libcore/ptr/const_ptr.rs

@@ -659,8 +659,8 @@ impl<T: ?Sized> *const T {
     /// `align`.
     ///
     /// If it is not possible to align the pointer, the implementation returns
-    /// `usize::max_value()`. It is permissible for the implementation to *always*
-    /// return `usize::max_value()`. Only your algorithm's performance can depend
+    /// `usize::MAX`. It is permissible for the implementation to *always*
+    /// return `usize::MAX`. Only your algorithm's performance can depend
     /// on getting a usable offset here, not its correctness.
     ///
     /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be

Diff for: src/libcore/ptr/mut_ptr.rs

@@ -847,8 +847,8 @@ impl<T: ?Sized> *mut T {
     /// `align`.
     ///
     /// If it is not possible to align the pointer, the implementation returns
-    /// `usize::max_value()`. It is permissible for the implementation to *always*
-    /// return `usize::max_value()`. Only your algorithm's performance can depend
+    /// `usize::MAX`. It is permissible for the implementation to *always*
+    /// return `usize::MAX`. Only your algorithm's performance can depend
     /// on getting a usable offset here, not its correctness.
     ///
     /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be

Diff for: src/libcore/slice/mod.rs

@@ -2588,7 +2588,7 @@ impl<T> [T] {
     /// assert!(![1, 3, 2, 4].is_sorted());
     /// assert!([0].is_sorted());
     /// assert!(empty.is_sorted());
-    /// assert!(![0.0, 1.0, std::f32::NAN].is_sorted());
+    /// assert!(![0.0, 1.0, f32::NAN].is_sorted());
     /// ```
     #[inline]
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]

Diff for: src/libcore/time.rs

@@ -389,7 +389,7 @@ impl Duration {
     /// use std::time::Duration;
     ///
     /// assert_eq!(Duration::new(0, 0).checked_add(Duration::new(0, 1)), Some(Duration::new(0, 1)));
-    /// assert_eq!(Duration::new(1, 0).checked_add(Duration::new(std::u64::MAX, 0)), None);
+    /// assert_eq!(Duration::new(1, 0).checked_add(Duration::new(u64::MAX, 0)), None);
     /// ```
     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
     #[inline]
@@ -460,7 +460,7 @@ impl Duration {
     /// use std::time::Duration;
     ///
     /// assert_eq!(Duration::new(0, 500_000_001).checked_mul(2), Some(Duration::new(1, 2)));
-    /// assert_eq!(Duration::new(std::u64::MAX - 1, 0).checked_mul(2), None);
+    /// assert_eq!(Duration::new(u64::MAX - 1, 0).checked_mul(2), None);
     /// ```
     #[stable(feature = "duration_checked_ops", since = "1.16.0")]
     #[inline]

Diff for: src/librustc_ast_lowering/item.rs

@@ -972,8 +972,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
     ) -> hir::BodyId {
         let prev_gen_kind = self.generator_kind.take();
+        let task_context = self.task_context.take();
         let (parameters, result) = f(self);
         let body_id = self.record_body(parameters, result);
+        self.task_context = task_context;
         self.generator_kind = prev_gen_kind;
         body_id
     }

Diff for: src/librustc_codegen_llvm/consts.rs

@@ -436,24 +436,21 @@ impl StaticMethods for CodegenCx<'ll, 'tcx> {
                 //
                 // We could remove this hack whenever we decide to drop macOS 10.10 support.
                 if self.tcx.sess.target.target.options.is_like_osx {
-                    assert_eq!(alloc.relocations().len(), 0);
-
-                    let is_zeroed = {
-                        // Treats undefined bytes as if they were defined with the byte value that
-                        // happens to be currently assigned in mir. This is valid since reading
-                        // undef bytes may yield arbitrary values.
-                        //
-                        // FIXME: ignore undef bytes even with representation `!= 0`.
-                        //
-                        // The `inspect` method is okay here because we checked relocations, and
-                        // because we are doing this access to inspect the final interpreter state
-                        // (not as part of the interpreter execution).
-                        alloc
+                    // The `inspect` method is okay here because we checked relocations, and
+                    // because we are doing this access to inspect the final interpreter state
+                    // (not as part of the interpreter execution).
+                    //
+                    // FIXME: This check requires that the (arbitrary) value of undefined bytes
+                    // happens to be zero. Instead, we should only check the value of defined bytes
+                    // and set all undefined bytes to zero if this allocation is headed for the
+                    // BSS.
+                    let all_bytes_are_zero = alloc.relocations().is_empty()
+                        && alloc
                             .inspect_with_undef_and_ptr_outside_interpreter(0..alloc.len())
                             .iter()
-                            .all(|b| *b == 0)
-                    };
-                    let sect_name = if is_zeroed {
+                            .all(|&byte| byte == 0);
+
+                    let sect_name = if all_bytes_are_zero {
                         CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_bss\0")
                     } else {
                         CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_data\0")

Diff for: src/librustc_error_codes/error_codes/E0502.md

@@ -1,5 +1,4 @@
-This error indicates that you are trying to borrow a variable as mutable when it
-has already been borrowed as immutable.
+A variable already borrowed as immutable was borrowed as mutable.
 
 Erroneous code example:
 

Diff for: src/librustc_infer/traits/mod.rs

@@ -6,7 +6,7 @@ mod engine;
 pub mod error_reporting;
 mod project;
 mod structural_impls;
-mod util;
+pub mod util;
 
 use rustc_hir as hir;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};

Diff for: src/librustc_infer/traits/util.rs

@@ -2,9 +2,12 @@ use smallvec::smallvec;
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::ty::outlives::Component;
-use rustc_middle::ty::{self, ToPolyTraitRef, TyCtxt};
+use rustc_middle::ty::{self, ToPolyTraitRef, ToPredicate, TyCtxt, WithConstness};
 
-fn anonymize_predicate<'tcx>(tcx: TyCtxt<'tcx>, pred: &ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
+pub fn anonymize_predicate<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    pred: &ty::Predicate<'tcx>,
+) -> ty::Predicate<'tcx> {
     match *pred {
         ty::Predicate::Trait(ref data, constness) => {
             ty::Predicate::Trait(tcx.anonymize_late_bound_regions(data), constness)
@@ -88,6 +91,21 @@ pub struct Elaborator<'tcx> {
     visited: PredicateSet<'tcx>,
 }
 
+pub fn elaborate_trait_ref<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    trait_ref: ty::PolyTraitRef<'tcx>,
+) -> Elaborator<'tcx> {
+    elaborate_predicates(tcx, vec![trait_ref.without_const().to_predicate()])
+}
+
+pub fn elaborate_trait_refs<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
+) -> Elaborator<'tcx> {
+    let predicates = trait_refs.map(|trait_ref| trait_ref.without_const().to_predicate()).collect();
+    elaborate_predicates(tcx, predicates)
+}
+
 pub fn elaborate_predicates<'tcx>(
     tcx: TyCtxt<'tcx>,
     mut predicates: Vec<ty::Predicate<'tcx>>,
@@ -98,6 +116,10 @@ pub fn elaborate_predicates<'tcx>(
 }
 
 impl Elaborator<'tcx> {
+    pub fn filter_to_traits(self) -> FilterToTraits<Self> {
+        FilterToTraits::new(self)
+    }
+
     fn elaborate(&mut self, predicate: &ty::Predicate<'tcx>) {
         let tcx = self.visited.tcx;
         match *predicate {
@@ -223,3 +245,57 @@ impl Iterator for Elaborator<'tcx> {
         }
     }
 }
+
+///////////////////////////////////////////////////////////////////////////
+// Supertrait iterator
+///////////////////////////////////////////////////////////////////////////
+
+pub type Supertraits<'tcx> = FilterToTraits<Elaborator<'tcx>>;
+
+pub fn supertraits<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    trait_ref: ty::PolyTraitRef<'tcx>,
+) -> Supertraits<'tcx> {
+    elaborate_trait_ref(tcx, trait_ref).filter_to_traits()
+}
+
+pub fn transitive_bounds<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
+) -> Supertraits<'tcx> {
+    elaborate_trait_refs(tcx, bounds).filter_to_traits()
+}
+
+///////////////////////////////////////////////////////////////////////////
+// Other
+///////////////////////////////////////////////////////////////////////////
+
+/// A filter around an iterator of predicates that makes it yield up
+/// just trait references.
+pub struct FilterToTraits<I> {
+    base_iterator: I,
+}
+
+impl<I> FilterToTraits<I> {
+    fn new(base: I) -> FilterToTraits<I> {
+        FilterToTraits { base_iterator: base }
+    }
+}
+
+impl<'tcx, I: Iterator<Item = ty::Predicate<'tcx>>> Iterator for FilterToTraits<I> {
+    type Item = ty::PolyTraitRef<'tcx>;
+
+    fn next(&mut self) -> Option<ty::PolyTraitRef<'tcx>> {
+        while let Some(pred) = self.base_iterator.next() {
+            if let ty::Predicate::Trait(data, _) = pred {
+                return Some(data.to_poly_trait_ref());
+            }
+        }
+        None
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let (_, upper) = self.base_iterator.size_hint();
+        (0, upper)
+    }
+}