Elaborate safety comment;

Author: bjoernager

library/core/src/char/methods.rs

@@ -1788,7 +1788,7 @@ pub const fn encode_utf8_raw(code: u32, dst: &mut [u8]) -> &mut [u8] {
         // Note that the original message is not const-compatible due to formatting.
         _ => panic!("encode_utf8: buffer does not have enough bytes to encode code point"),
     };
-    // SAFETY: `<&mut [u8]>::as_mut_ptr` returns a valid pointer and `len` has been tested to be valid.
+    // SAFETY: `<&mut [u8]>::as_mut_ptr` is guaranteed to return a valid pointer and `len` has been tested to be within bounds.
     unsafe { slice::from_raw_parts_mut(dst.as_mut_ptr(), len) }
 }
 

library/core/src/lib.rs

@@ -118,8 +118,8 @@
 #![feature(const_array_into_iter_constructors)]
 #![feature(const_bigint_helper_methods)]
 #![feature(const_black_box)]
-#![feature(const_char_encode_utf8)]
 #![feature(const_cell_into_inner)]
+#![feature(const_char_encode_utf8)]
 #![feature(const_eval_select)]
 #![feature(const_exact_div)]
 #![feature(const_float_classify)]