Mark str::to_uppercase and str::to_lowercase as stable.

src/libcollections/str.rs

@@ -1851,7 +1851,7 @@ impl str {
     /// let s = "HELLO";
     /// assert_eq!(s.to_lowercase(), "hello");
     /// ```
-    #[unstable(feature = "collections")]
+    #[stable(feature = "unicode_case_mapping", since = "1.2.0")]
     pub fn to_lowercase(&self) -> String {
         let mut s = String::with_capacity(self.len());
         for (i, c) in self[..].char_indices() {
@@ -1892,7 +1892,7 @@ impl str {
     /// let s = "hello";
     /// assert_eq!(s.to_uppercase(), "HELLO");
     /// ```
-    #[unstable(feature = "collections")]
+    #[stable(feature = "unicode_case_mapping", since = "1.2.0")]
     pub fn to_uppercase(&self) -> String {
         let mut s = String::with_capacity(self.len());
         s.extend(self[..].chars().flat_map(|c| c.to_uppercase()));

src/librustc_unicode/char.rs

@@ -70,10 +70,10 @@ impl Iterator for ToUppercase {
 /// An iterator over the titlecase mapping of a given character, returned from
 /// the [`to_titlecase` method](../primitive.char.html#method.to_titlecase) on
 /// characters.
-#[stable(feature = "char_to_titlecase", since = "1.2.0")]
+#[stable(feature = "unicode_case_mapping", since = "1.2.0")]
 pub struct ToTitlecase(CaseMappingIter);
 
-#[stable(feature = "char_to_titlecase", since = "1.2.0")]
+#[stable(feature = "unicode_case_mapping", since = "1.2.0")]
 impl Iterator for ToTitlecase {
     type Item = char;
     fn next(&mut self) -> Option<char> { self.0.next() }
@@ -481,7 +481,7 @@ impl char {
     /// Returns an iterator which yields the characters corresponding to the
     /// lowercase equivalent of the character. If no conversion is possible then
     /// an iterator with just the input character is returned.
-    #[stable(feature = "char_to_titlecase", since = "1.2.0")]
+    #[stable(feature = "unicode_case_mapping", since = "1.2.0")]
     #[inline]
     pub fn to_titlecase(self) -> ToTitlecase {
         ToTitlecase(CaseMappingIter::new(conversions::to_title(self)))