Rollup merge of rust-lang#82120 - sfackler:arguments-as-str, r=dtolnay

Stabilize Arguments::as_str

Closes rust-lang#74442

Author: JohnTitor

library/core/src/fmt/mod.rs

@@ -401,8 +401,6 @@ impl<'a> Arguments<'a> {
     /// # Examples
     ///
     /// ```rust
-    /// #![feature(fmt_as_str)]
-    ///
     /// use std::fmt::Arguments;
     ///
     /// fn write_str(_: &str) { /* ... */ }
@@ -417,13 +415,11 @@ impl<'a> Arguments<'a> {
     /// ```
     ///
     /// ```rust
-    /// #![feature(fmt_as_str)]
-    ///
     /// assert_eq!(format_args!("hello").as_str(), Some("hello"));
     /// assert_eq!(format_args!("").as_str(), Some(""));
     /// assert_eq!(format_args!("{}", 1).as_str(), None);
     /// ```
-    #[unstable(feature = "fmt_as_str", issue = "74442")]
+    #[stable(feature = "fmt_as_str", since = "1.52.0")]
     #[inline]
     pub fn as_str(&self) -> Option<&'static str> {
         match (self.pieces, self.args) {

library/std/src/lib.rs

@@ -264,7 +264,6 @@
 #![feature(exhaustive_patterns)]
 #![feature(extend_one)]
 #![feature(external_doc)]
-#![feature(fmt_as_str)]
 #![feature(fn_traits)]
 #![feature(format_args_nl)]
 #![feature(gen_future)]