Rollup merge of #118811 - EbbDrop:is-sorted-by-bool, r=Mark-Simulacrum

Use `bool` instead of `PartiolOrd` as return value of the comparison closure in `{slice,Iteraotr}::is_sorted_by`

Changes the function signature of the closure given to `{slice,Iteraotr}::is_sorted_by` to return a `bool` instead of a `PartiolOrd` as suggested by the libs-api team here: https://github.com/rust-lang/rust/issues/53485#issuecomment-1766411980.

This means these functions now return true if the closure returns true for all the pairs of values.

6 files changed, 37 insertions, 26 deletions

diff --git a/compiler/rustc_monomorphize/src/partitioning.rs b/compiler/rustc_monomorphize/src/partitioning.rs
index 2c40cd4d8f2..7ff182381b8 100644
--- a/compiler/rustc_monomorphize/src/partitioning.rs
+++ b/compiler/rustc_monomorphize/src/partitioning.rs
@@ -182,7 +182,7 @@ where
     }
 
     // Ensure CGUs are sorted by name, so that we get deterministic results.
-    if !codegen_units.is_sorted_by(|a, b| Some(a.name().as_str().cmp(b.name().as_str()))) {
+    if !codegen_units.is_sorted_by(|a, b| a.name().as_str() <= b.name().as_str()) {
         let mut names = String::new();
         for cgu in codegen_units.iter() {
             names += &format!("- {}\n", cgu.name());
@@ -317,7 +317,7 @@ fn merge_codegen_units<'tcx>(
     assert!(cx.tcx.sess.codegen_units().as_usize() >= 1);
 
     // A sorted order here ensures merging is deterministic.
-    assert!(codegen_units.is_sorted_by(|a, b| Some(a.name().as_str().cmp(b.name().as_str()))));
+    assert!(codegen_units.is_sorted_by(|a, b| a.name().as_str() <= b.name().as_str()));
 
     // This map keeps track of what got merged into what.
     let mut cgu_contents: FxHashMap<Symbol, Vec<Symbol>> =
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index d94a508b5b2..83f8fd25b50 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -4033,42 +4033,42 @@ pub trait Iterator {
         Self: Sized,
         Self::Item: PartialOrd,
     {
-        self.is_sorted_by(PartialOrd::partial_cmp)
+        self.is_sorted_by(|a, b| a <= b)
     }
 
     /// Checks if the elements of this iterator are sorted using the given comparator function.
     ///
     /// Instead of using `PartialOrd::partial_cmp`, this function uses the given `compare`
-    /// function to determine the ordering of two elements. Apart from that, it's equivalent to
-    /// [`is_sorted`]; see its documentation for more information.
+    /// function to determine whether two elements are to be considered in sorted order.
     ///
     /// # Examples
     ///
     /// ```
     /// #![feature(is_sorted)]
     ///
-    /// assert!([1, 2, 2, 9].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
-    /// 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, f32::NAN].iter().is_sorted_by(|a, b| a.partial_cmp(b)));
-    /// ```
+    /// assert!([1, 2, 2, 9].iter().is_sorted_by(|a, b| a <= b));
+    /// assert!(![1, 2, 2, 9].iter().is_sorted_by(|a, b| a < b));
     ///
-    /// [`is_sorted`]: Iterator::is_sorted
+    /// assert!([0].iter().is_sorted_by(|a, b| true));
+    /// assert!([0].iter().is_sorted_by(|a, b| false));
+    ///
+    /// assert!(std::iter::empty::<i32>().is_sorted_by(|a, b| false));
+    /// assert!(std::iter::empty::<i32>().is_sorted_by(|a, b| true));
+    /// ```
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
     #[rustc_do_not_const_check]
     fn is_sorted_by<F>(mut self, compare: F) -> bool
     where
         Self: Sized,
-        F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
+        F: FnMut(&Self::Item, &Self::Item) -> bool,
     {
         #[inline]
         fn check<'a, T>(
             last: &'a mut T,
-            mut compare: impl FnMut(&T, &T) -> Option<Ordering> + 'a,
+            mut compare: impl FnMut(&T, &T) -> bool + 'a,
         ) -> impl FnMut(T) -> bool + 'a {
             move |curr| {
-                if let Some(Ordering::Greater) | None = compare(&last, &curr) {
+                if !compare(&last, &curr) {
                     return false;
                 }
                 *last = curr;
diff --git a/library/core/src/slice/iter.rs b/library/core/src/slice/iter.rs
index 4a64faf9b3f..cd9e18d1a2d 100644
--- a/library/core/src/slice/iter.rs
+++ b/library/core/src/slice/iter.rs
@@ -4,7 +4,6 @@
 mod macros;
 
 use crate::cmp;
-use crate::cmp::Ordering;
 use crate::fmt;
 use crate::intrinsics::assume;
 use crate::iter::{
@@ -133,7 +132,7 @@ iterator! {struct Iter -> *const T, &'a T, const, {/* no mut */}, as_ref, {
     fn is_sorted_by<F>(self, mut compare: F) -> bool
     where
         Self: Sized,
-        F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
+        F: FnMut(&Self::Item, &Self::Item) -> bool,
     {
         self.as_slice().is_sorted_by(|a, b| compare(&a, &b))
     }
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index ee36d93576b..c191877c434 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -3957,23 +3957,36 @@ impl<T> [T] {
     where
         T: PartialOrd,
     {
-        self.is_sorted_by(|a, b| a.partial_cmp(b))
+        self.is_sorted_by(|a, b| a <= b)
     }
 
     /// Checks if the elements of this slice are sorted using the given comparator function.
     ///
     /// Instead of using `PartialOrd::partial_cmp`, this function uses the given `compare`
-    /// function to determine the ordering of two elements. Apart from that, it's equivalent to
-    /// [`is_sorted`]; see its documentation for more information.
+    /// function to determine whether two elements are to be considered in sorted order.
     ///
-    /// [`is_sorted`]: slice::is_sorted
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(is_sorted)]
+    ///
+    /// assert!([1, 2, 2, 9].is_sorted_by(|a, b| a <= b));
+    /// assert!(![1, 2, 2, 9].is_sorted_by(|a, b| a < b));
+    ///
+    /// assert!([0].is_sorted_by(|a, b| true));
+    /// assert!([0].is_sorted_by(|a, b| false));
+    ///
+    /// let empty: [i32; 0] = [];
+    /// assert!(empty.is_sorted_by(|a, b| false));
+    /// assert!(empty.is_sorted_by(|a, b| true));
+    /// ```
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
     #[must_use]
     pub fn is_sorted_by<'a, F>(&'a self, mut compare: F) -> bool
     where
-        F: FnMut(&'a T, &'a T) -> Option<Ordering>,
+        F: FnMut(&'a T, &'a T) -> bool,
     {
-        self.array_windows().all(|[a, b]| compare(a, b).map_or(false, Ordering::is_le))
+        self.array_windows().all(|[a, b]| compare(a, b))
     }
 
     /// Checks if the elements of this slice are sorted using the given key extraction function.
diff --git a/library/core/tests/iter/traits/iterator.rs b/library/core/tests/iter/traits/iterator.rs
index 9c1dce7b66d..4c2d843eaa0 100644
--- a/library/core/tests/iter/traits/iterator.rs
+++ b/library/core/tests/iter/traits/iterator.rs
@@ -1,4 +1,3 @@
-use core::cmp::Ordering;
 use core::num::NonZeroUsize;
 
 /// A wrapper struct that implements `Eq` and `Ord` based on the wrapped
@@ -408,7 +407,7 @@ fn test_is_sorted() {
 
     // Tests for is_sorted_by
     assert!(![6, 2, 8, 5, 1, -60, 1337].iter().is_sorted());
-    assert!([6, 2, 8, 5, 1, -60, 1337].iter().is_sorted_by(|_, _| Some(Ordering::Less)));
+    assert!([6, 2, 8, 5, 1, -60, 1337].iter().is_sorted_by(|_, _| true));
 
     // Tests for is_sorted_by_key
     assert!([-2, -1, 0, 3].iter().is_sorted());
diff --git a/library/core/tests/slice.rs b/library/core/tests/slice.rs
index c7a5feb04ae..bcf7b5e5977 100644
--- a/library/core/tests/slice.rs
+++ b/library/core/tests/slice.rs
@@ -2307,7 +2307,7 @@ fn test_is_sorted() {
 
     // Tests for is_sorted_by
     assert!(![6, 2, 8, 5, 1, -60, 1337].is_sorted());
-    assert!([6, 2, 8, 5, 1, -60, 1337].is_sorted_by(|_, _| Some(Ordering::Less)));
+    assert!([6, 2, 8, 5, 1, -60, 1337].is_sorted_by(|_, _| true));
 
     // Tests for is_sorted_by_key
     assert!([-2, -1, 0, 3].is_sorted());