Stabilize Option::deref and Option::deref_mut

The tracking issue https://github.com/rust-lang/rust/issues/50264
still has unresolved question for the corresponding `Result` methods.

src/libcore/option.rs

@@ -1102,7 +1102,6 @@ impl<T: Default> Option<T> {
     }
 }
 
-#[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
 impl<T: Deref> Option<T> {
     /// Converts from `Option<T>` (or `&Option<T>`) to `Option<&T::Target>`.
     ///
@@ -1114,20 +1113,18 @@ impl<T: Deref> Option<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(inner_deref)]
-    ///
     /// let x: Option<String> = Some("hey".to_owned());
     /// assert_eq!(x.as_deref(), Some("hey"));
     ///
     /// let x: Option<String> = None;
     /// assert_eq!(x.as_deref(), None);
     /// ```
+    #[stable(feature = "option_deref", since = "1.40.0")]
     pub fn as_deref(&self) -> Option<&T::Target> {
         self.as_ref().map(|t| t.deref())
     }
 }
 
-#[unstable(feature = "inner_deref", reason = "newly added", issue = "50264")]
 impl<T: DerefMut> Option<T> {
     /// Converts from `Option<T>` (or `&mut Option<T>`) to `Option<&mut T::Target>`.
     ///
@@ -1137,14 +1134,13 @@ impl<T: DerefMut> Option<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(inner_deref)]
-    ///
     /// let mut x: Option<String> = Some("hey".to_owned());
     /// assert_eq!(x.as_deref_mut().map(|x| {
     ///     x.make_ascii_uppercase();
     ///     x
     /// }), Some("HEY".to_owned().as_mut_str()));
     /// ```
+    #[stable(feature = "option_deref", since = "1.40.0")]
     pub fn as_deref_mut(&mut self) -> Option<&mut T::Target> {
         self.as_mut().map(|t| t.deref_mut())
     }

src/librustc/lib.rs

@@ -35,7 +35,6 @@
 #![feature(const_transmute)]
 #![feature(core_intrinsics)]
 #![feature(drain_filter)]
-#![feature(inner_deref)]
 #![cfg_attr(windows, feature(libc))]
 #![feature(never_type)]
 #![feature(exhaustive_patterns)]

src/librustc_resolve/lib.rs

@@ -9,7 +9,6 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 
-#![feature(inner_deref)]
 #![feature(crate_visibility_modifier)]
 #![feature(label_break_value)]
 #![feature(mem_take)]

src/librustc_save_analysis/lib.rs

@@ -1,6 +1,5 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(nll)]
-#![feature(inner_deref)]
 
 #![recursion_limit="256"]
 

src/librustc_typeck/lib.rs

@@ -67,7 +67,6 @@ This API is completely unstable and subject to change.
 #![feature(nll)]
 #![feature(slice_patterns)]
 #![feature(never_type)]
-#![feature(inner_deref)]
 #![feature(mem_take)]
 
 #![recursion_limit="256"]

src/librustdoc/lib.rs

@@ -15,7 +15,6 @@
 #![feature(crate_visibility_modifier)]
 #![feature(const_fn)]
 #![feature(drain_filter)]
-#![feature(inner_deref)]
 #![feature(never_type)]
 #![feature(mem_take)]
 #![feature(unicode_internals)]

src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref.rs

@@ -1,5 +1,3 @@
-#![feature(inner_deref)]
-
 fn main() {
     let _result = &Some(42).as_deref();
 //~^ ERROR no method named `as_deref` found for type `std::option::Option<{integer}>`

src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref.stderr

@@ -1,5 +1,5 @@
 error[E0599]: no method named `as_deref` found for type `std::option::Option<{integer}>` in the current scope
-  --> $DIR/option-as_deref.rs:4:29
+  --> $DIR/option-as_deref.rs:2:29
    |
 LL |     let _result = &Some(42).as_deref();
    |                             ^^^^^^^^ help: there is a method with a similar name: `as_ref`

src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref_mut.rs

@@ -1,5 +1,3 @@
-#![feature(inner_deref)]
-
 fn main() {
     let _result = &mut Some(42).as_deref_mut();
 //~^ ERROR no method named `as_deref_mut` found for type `std::option::Option<{integer}>`

src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref_mut.stderr

@@ -1,5 +1,5 @@
 error[E0599]: no method named `as_deref_mut` found for type `std::option::Option<{integer}>` in the current scope
-  --> $DIR/option-as_deref_mut.rs:4:33
+  --> $DIR/option-as_deref_mut.rs:2:33
    |
 LL |     let _result = &mut Some(42).as_deref_mut();
    |                                 ^^^^^^^^^^^^ method not found in `std::option::Option<{integer}>`