Rollup merge of rust-lang#86794 - inquisitivecrystal:seek-rewind, r=m-ou-se

Stabilize `Seek::rewind()`

This stabilizes `Seek::rewind`. It seemed to fit into one of the existing tests, so I extended that test rather than adding a new one.

Closes rust-lang#85149.

Author: JohnTitor

Diff for: library/std/src/io/mod.rs

@@ -1759,7 +1759,6 @@ pub trait Seek {
     /// # Example
     ///
     /// ```no_run
-    /// #![feature(seek_rewind)]
     /// use std::io::{Read, Seek, Write};
     /// use std::fs::OpenOptions;
     ///
@@ -1777,7 +1776,7 @@ pub trait Seek {
     /// f.read_to_string(&mut buf).unwrap();
     /// assert_eq!(&buf, hello);
     /// ```
-    #[unstable(feature = "seek_rewind", issue = "85149")]
+    #[stable(feature = "seek_rewind", since = "1.55.0")]
     fn rewind(&mut self) -> Result<()> {
         self.seek(SeekFrom::Start(0))?;
         Ok(())

Diff for: library/std/src/io/tests.rs

@@ -336,6 +336,10 @@ fn seek_position() -> io::Result<()> {
     assert_eq!(c.stream_position()?, 8);
     assert_eq!(c.stream_position()?, 8);
 
+    c.rewind()?;
+    assert_eq!(c.stream_position()?, 0);
+    assert_eq!(c.stream_position()?, 0);
+
     Ok(())
 }