Stabilize exact_size_is_empty feature

Author: tesuji

src/liballoc/lib.rs

@@ -89,7 +89,6 @@
 #![feature(core_intrinsics)]
 #![feature(container_error_extra)]
 #![feature(dropck_eyepatch)]
-#![feature(exact_size_is_empty)]
 #![feature(fmt_internals)]
 #![feature(fn_traits)]
 #![feature(fundamental)]

src/liballoc/tests/lib.rs

@@ -1,7 +1,6 @@
 #![feature(allocator_api)]
 #![feature(box_syntax)]
 #![feature(drain_filter)]
-#![feature(exact_size_is_empty)]
 #![feature(new_uninit)]
 #![feature(option_flattening)]
 #![feature(pattern)]

src/libcore/iter/traits/exact_size.rs

@@ -114,8 +114,6 @@ pub trait ExactSizeIterator: Iterator {
     /// Basic usage:
     ///
     /// ```
-    /// #![feature(exact_size_is_empty)]
-    ///
     /// let mut one_element = std::iter::once(0);
     /// assert!(!one_element.is_empty());
     ///
@@ -125,7 +123,7 @@ pub trait ExactSizeIterator: Iterator {
     /// assert_eq!(one_element.next(), None);
     /// ```
     #[inline]
-    #[unstable(feature = "exact_size_is_empty", issue = "35428")]
+    #[stable(feature = "exact_size_is_empty", since = "1.40.0")]
     fn is_empty(&self) -> bool {
         self.len() == 0
     }

src/libcore/tests/lib.rs

@@ -6,7 +6,6 @@
 #![feature(core_private_diy_float)]
 #![feature(debug_map_key_value)]
 #![feature(dec2flt)]
-#![feature(exact_size_is_empty)]
 #![feature(fixed_size_array)]
 #![feature(flt2dec)]
 #![feature(fmt_internals)]

src/libstd/lib.rs

@@ -258,7 +258,6 @@
 #![feature(doc_spotlight)]
 #![feature(dropck_eyepatch)]
 #![feature(duration_constants)]
-#![feature(exact_size_is_empty)]
 #![feature(exhaustive_patterns)]
 #![feature(external_doc)]
 #![feature(fn_traits)]