Rollup merge of rust-lang#31831 - tormol:master, r=alexcrichton

The "A buffer that's too small" example was calling encode_utf**8**().

src/librustc_unicode/char.rs

@@ -457,26 +457,26 @@ impl char {
     ///
     /// # Examples
     ///
-    /// In both of these examples, 'ß' takes one `u16` to encode.
+    /// In both of these examples, '𝕊' takes two `u16`s to encode.
     ///
     /// ```
     /// #![feature(unicode)]
     ///
-    /// let mut b = [0; 1];
+    /// let mut b = [0; 2];
     ///
-    /// let result = 'ß'.encode_utf16(&mut b);
+    /// let result = '𝕊'.encode_utf16(&mut b);
     ///
-    /// assert_eq!(result, Some(1));
+    /// assert_eq!(result, Some(2));
     /// ```
     ///
     /// A buffer that's too small:
     ///
     /// ```
     /// #![feature(unicode)]
     ///
-    /// let mut b = [0; 0];
+    /// let mut b = [0; 1];
     ///
-    /// let result = 'ß'.encode_utf8(&mut b);
+    /// let result = '𝕊'.encode_utf16(&mut b);
     ///
     /// assert_eq!(result, None);
     /// ```