std: Stabilize the str_{mut,box}_extras feature

Stabilizes

* `<&mut str>::as_bytes_mut`
* `<Box<str>>::into_boxed_bytes`
* `std::str::from_boxed_utf8_unchecked`
* `std::str::from_utf8_mut`
* `std::str::from_utf8_unchecked_mut`

Closes #41119

src/liballoc/lib.rs

@@ -115,7 +115,6 @@
 #![feature(specialization)]
 #![feature(staged_api)]
 #![feature(str_internals)]
-#![feature(str_mut_extras)]
 #![feature(trusted_len)]
 #![feature(unboxed_closures)]
 #![feature(unicode)]

src/liballoc/str.rs

@@ -290,7 +290,7 @@ impl str {
     }
 
     /// Converts a mutable string slice to a mutable byte slice.
-    #[unstable(feature = "str_mut_extras", issue = "41119")]
+    #[stable(feature = "str_mut_extras", since = "1.20.0")]
     #[inline(always)]
     pub unsafe fn as_bytes_mut(&mut self) -> &mut [u8] {
         core_str::StrExt::as_bytes_mut(self)
@@ -1725,7 +1725,7 @@ impl str {
     }
 
     /// Converts a `Box<str>` into a `Box<[u8]>` without copying or allocating.
-    #[unstable(feature = "str_box_extras", issue = "41119")]
+    #[stable(feature = "str_box_extras", since = "1.20.0")]
     pub fn into_boxed_bytes(self: Box<str>) -> Box<[u8]> {
         self.into()
     }
@@ -1992,7 +1992,7 @@ impl str {
 
 /// Converts a boxed slice of bytes to a boxed string slice without checking
 /// that the string contains valid UTF-8.
-#[unstable(feature = "str_box_extras", issue = "41119")]
+#[stable(feature = "str_box_extras", since = "1.20.0")]
 pub unsafe fn from_boxed_utf8_unchecked(v: Box<[u8]>) -> Box<str> {
     mem::transmute(v)
 }

src/libcore/str/mod.rs

@@ -301,7 +301,7 @@ pub fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
 }
 
 /// Converts a mutable slice of bytes to a mutable string slice.
-#[unstable(feature = "str_mut_extras", issue = "41119")]
+#[stable(feature = "str_mut_extras", since = "1.20.0")]
 pub fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> {
     run_utf8_validation(v)?;
     Ok(unsafe { from_utf8_unchecked_mut(v) })
@@ -382,7 +382,7 @@ pub unsafe fn from_utf8_unchecked(v: &[u8]) -> &str {
 ///
 /// [fromutf8]: fn.from_utf8_unchecked.html
 #[inline]
-#[unstable(feature = "str_mut_extras", issue = "41119")]
+#[stable(feature = "str_mut_extras", since = "1.20.0")]
 pub unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str {
     mem::transmute(v)
 }
@@ -2123,7 +2123,7 @@ pub trait StrExt {
     fn is_char_boundary(&self, index: usize) -> bool;
     #[stable(feature = "core", since = "1.6.0")]
     fn as_bytes(&self) -> &[u8];
-    #[unstable(feature = "str_mut_extras", issue = "41119")]
+    #[stable(feature = "str_mut_extras", since = "1.20.0")]
     unsafe fn as_bytes_mut(&mut self) -> &mut [u8];
     #[stable(feature = "core", since = "1.6.0")]
     fn find<'a, P: Pattern<'a>>(&'a self, pat: P) -> Option<usize>;

src/libstd/ffi/c_str.rs

@@ -453,8 +453,6 @@ impl CString {
     /// # Examples
     ///
     /// ```
-    /// #![feature(as_c_str)]
-    ///
     /// use std::ffi::{CString, CStr};
     ///
     /// let c_string = CString::new(b"foo".to_vec()).unwrap();
@@ -474,8 +472,6 @@ impl CString {
     /// # Examples
     ///
     /// ```
-    /// #![feature(into_boxed_c_str)]
-    ///
     /// use std::ffi::{CString, CStr};
     ///
     /// let c_string = CString::new(b"foo".to_vec()).unwrap();
@@ -1001,8 +997,6 @@ impl CStr {
     /// # Examples
     ///
     /// ```
-    /// #![feature(into_boxed_c_str)]
-    ///
     /// use std::ffi::CString;
     ///
     /// let c_string = CString::new(b"foo".to_vec()).unwrap();

src/libstd/ffi/os_str.rs

@@ -252,8 +252,6 @@ impl OsString {
     /// # Examples
     ///
     /// ```
-    /// #![feature(into_boxed_os_str)]
-    ///
     /// use std::ffi::{OsString, OsStr};
     ///
     /// let s = OsString::from("hello");

src/libstd/lib.rs

@@ -303,7 +303,6 @@
 #![feature(stmt_expr_attributes)]
 #![feature(str_char)]
 #![feature(str_internals)]
-#![feature(str_mut_extras)]
 #![feature(str_utf16)]
 #![feature(test, rustc_private)]
 #![feature(thread_local)]