stdlib: remove is_sorted_by backport

The backport is no longer necessary with our new MSRV.

Part of #11964

src/builtins/fish_indent.rs

@@ -24,7 +24,7 @@
 use crate::env::environment::Environment;
 use crate::expand::INTERNAL_SEPARATOR;
 #[allow(unused_imports)]
-use crate::future::{IsSomeAnd, IsSorted};
+use crate::future::IsSomeAnd;
 use crate::future_feature_flags;
 use crate::global_safety::RelaxedAtomicBool;
 use crate::highlight::{HighlightRole, HighlightSpec, colorize, highlight_shell};
@@ -213,7 +213,7 @@ fn prettify(&mut self) -> WString {
     // Return the gap ranges from our ast.
     fn compute_gaps(&self) -> Vec<SourceRange> {
         let range_compare = |r1: SourceRange, r2: SourceRange| {
-            (r1.start(), r1.length()).cmp(&(r2.start(), r2.length()))
+            (r1.start(), r1.length()) <= (r2.start(), r2.length())
         };
         // Collect the token ranges into a list.
         let mut tok_ranges = vec![];
@@ -229,7 +229,7 @@ fn compute_gaps(&self) -> Vec<SourceRange> {
         tok_ranges.push(SourceRange::new(self.state.source.len(), 0));
 
         // Our tokens should be sorted.
-        assert!(tok_ranges.is_sorted_by(|x, y| Some(range_compare(*x, *y))));
+        assert!(tok_ranges.is_sorted_by(|x, y| range_compare(*x, *y)));
 
         // For each range, add a gap range between the previous range and this range.
         let mut gaps = vec![];
@@ -369,7 +369,7 @@ fn compute_multi_line_brace_statement_locations(&self) -> Vec<usize> {
                 result.push(brace_statement.source_range().start());
             }
         }
-        assert!(result.is_sorted_by(|l, r| Some(l.cmp(r))));
+        assert!(result.is_sorted_by(|l, r| l <= r));
         result
     }
 }
@@ -587,7 +587,7 @@ fn range_contained_error(&self, r: SourceRange) -> bool {
         let range_is_before = |x: SourceRange, y: SourceRange| x.end().cmp(&y.start());
         // FIXME: We want to have the errors sorted, but in some cases they aren't.
         // I suspect this is when the ast is unwinding because the source is fudged up.
-        if errs.is_sorted_by(|&x, &y| Some(range_is_before(x, y))) {
+        if errs.is_sorted_by(|&x, &y| range_is_before(x, y).is_le()) {
             errs.partition_point(|&range| range_is_before(range, r).is_lt()) != errs.len()
         } else {
             false

src/future.rs

@@ -15,23 +15,3 @@ fn is_none_or(self, f: impl FnOnce(T) -> bool) -> bool {
         }
     }
 }
-
-// TODO(MSRV): is_sorted_by was added in rust 1.82
-pub trait IsSorted {
-    type T;
-    fn is_sorted_by(&self, pred: impl Fn(&Self::T, &Self::T) -> Option<std::cmp::Ordering>)
-    -> bool;
-}
-impl<T> IsSorted for &[T] {
-    type T = T;
-    fn is_sorted_by(&self, pred: impl Fn(&T, &T) -> Option<std::cmp::Ordering>) -> bool {
-        self.windows(2)
-            .all(|w| pred(&w[0], &w[1]).is_none_or(|order| order.is_le()))
-    }
-}
-impl<T> IsSorted for Vec<T> {
-    type T = T;
-    fn is_sorted_by(&self, pred: impl Fn(&T, &T) -> Option<std::cmp::Ordering>) -> bool {
-        IsSorted::is_sorted_by(&self.as_slice(), pred)
-    }
-}