Add is_sorted unstable documentation

Author: kleimkuhler

src/doc/unstable-book/src/library-features/is-sorted.md

@@ -0,0 +1,11 @@
+# `is_sorted`
+
+The tracking issue for this feature is: [#53485]
+
+[#53485]: https://github.com/rust-lang/rust/issues/53485
+
+------------------------
+
+Add the methods `is_sorted`, `is_sorted_by` and `is_sorted_by_key` to `[T]`;
+add the methods `is_sorted`, `is_sorted_by` and `is_sorted_by_key` to
+`Iterator`.

src/libcore/iter/iterator.rs

@@ -2626,6 +2626,7 @@ pub trait Iterator {
     /// assert!(std::iter::empty::<i32>().is_sorted());
     /// assert!(![0.0, 1.0, std::f32::NAN].iter().is_sorted());
     /// ```
+    #[inline]
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
     fn is_sorted(self) -> bool
     where
@@ -2676,6 +2677,7 @@ pub trait Iterator {
     /// assert!(["c", "bb", "aaa"].iter().is_sorted_by_key(|s| s.len()));
     /// assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
     /// ```
+    #[inline]
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
     fn is_sorted_by_key<F, K>(self, mut f: F) -> bool
     where

src/libcore/slice/mod.rs

@@ -2272,6 +2272,7 @@ impl<T> [T] {
     /// assert!(empty.is_sorted());
     /// assert!(![0.0, 1.0, std::f32::NAN].is_sorted());
     /// ```
+    #[inline]
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
     pub fn is_sorted(&self) -> bool
     where
@@ -2319,6 +2320,7 @@ impl<T> [T] {
     /// assert!(["c", "bb", "aaa"].is_sorted_by_key(|s| s.len()));
     /// assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));
     /// ```
+    #[inline]
     #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
     pub fn is_sorted_by_key<F, K>(&self, mut f: F) -> bool
     where

src/test/ui/feature-gates/feature-gate-is_sorted.rs

@@ -9,8 +9,15 @@
 // except according to those terms.
 
 fn main() {
+    // Assert `Iterator` methods are feature gated
     assert!([1, 2, 2, 9].iter().is_sorted());
     //^ ERROR: use of unstable library feature 'is_sorted'
     assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
     //^ ERROR: use of unstable library feature 'is_sorted'
+
+    // Assert `[T]` methods are feature gated
+    assert!([1, 2, 2, 9].is_sorted());
+    //^ ERROR: use of unstable library feature 'is_sorted'
+    assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));
+    //^ ERROR: use of unstable library feature 'is_sorted'
 }

src/test/ui/feature-gates/feature-gate-is_sorted.stderr

@@ -1,19 +1,35 @@
 error[E0658]: use of unstable library feature 'is_sorted': new API (see issue #53485)
-  --> $DIR/feature-gate-is_sorted.rs:12:33
+  --> $DIR/feature-gate-is_sorted.rs:13:33
    |
 LL |     assert!([1, 2, 2, 9].iter().is_sorted());
    |                                 ^^^^^^^^^
    |
    = help: add #![feature(is_sorted)] to the crate attributes to enable
 
 error[E0658]: use of unstable library feature 'is_sorted': new API (see issue #53485)
-  --> $DIR/feature-gate-is_sorted.rs:14:39
+  --> $DIR/feature-gate-is_sorted.rs:15:39
    |
 LL |     assert!(![-2i32, -1, 0, 3].iter().is_sorted_by_key(|n| n.abs()));
    |                                       ^^^^^^^^^^^^^^^^
    |
    = help: add #![feature(is_sorted)] to the crate attributes to enable
 
-error: aborting due to 2 previous errors
+error[E0658]: use of unstable library feature 'is_sorted': new API (see issue #53485)
+  --> $DIR/feature-gate-is_sorted.rs:19:26
+   |
+LL |     assert!([1, 2, 2, 9].is_sorted());
+   |                          ^^^^^^^^^
+   |
+   = help: add #![feature(is_sorted)] to the crate attributes to enable
+
+error[E0658]: use of unstable library feature 'is_sorted': new API (see issue #53485)
+  --> $DIR/feature-gate-is_sorted.rs:21:32
+   |
+LL |     assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));
+   |                                ^^^^^^^^^^^^^^^^
+   |
+   = help: add #![feature(is_sorted)] to the crate attributes to enable
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0658`.