Mark and implement 'make_ascii_uppercase' and 'make_ascii_lowercase' in '[u8]' and 'str' as const;

1 files changed, 14 insertions, 4 deletions

diff --git a/library/core/src/slice/ascii.rs b/library/core/src/slice/ascii.rs
index d1ea52fab6b..8f8050fdc3a 100644
--- a/library/core/src/slice/ascii.rs
+++ b/library/core/src/slice/ascii.rs
@@ -67,10 +67,15 @@ impl [u8] {
     ///
     /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+    #[rustc_const_unstable(feature = "const_make_ascii", issue = "130698")]
     #[inline]
-    pub fn make_ascii_uppercase(&mut self) {
-        for byte in self {
+    pub const fn make_ascii_uppercase(&mut self) {
+        // FIXME(const-hack): We would like to simply iterate using `for` loops but this isn't currently allowed in constant expressions.
+        let mut i = 0;
+        while i < self.len() {
+            let byte = &mut self[i];
             byte.make_ascii_uppercase();
+            i += 1;
         }
     }
 
@@ -84,10 +89,15 @@ impl [u8] {
     ///
     /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+    #[rustc_const_unstable(feature = "const_make_ascii", issue = "130698")]
     #[inline]
-    pub fn make_ascii_lowercase(&mut self) {
-        for byte in self {
+    pub const fn make_ascii_lowercase(&mut self) {
+        // FIXME(const-hack): We would like to simply iterate using `for` loops but this isn't currently allowed in constant expressions.
+        let mut i = 0;
+        while i < self.len() {
+            let byte = &mut self[i];
             byte.make_ascii_lowercase();
+            i += 1;
         }
     }