Fill in pointer cast type

Author: dtolnay

src/lib.rs

@@ -104,7 +104,7 @@ impl Buffer {
     /// representation within the buffer.
     #[cfg_attr(feature = "no-panic", no_panic)]
     pub fn format<I: Integer>(&mut self, i: I) -> &str {
-        let buf_ptr = self.bytes.as_mut_ptr().cast();
+        let buf_ptr = self.bytes.as_mut_ptr().cast::<I::Buffer>();
         let string = i.write(unsafe { &mut *buf_ptr });
         if string.len() > I::MAX_STR_LEN {
             unsafe { hint::unreachable_unchecked() };