Ignore new dead code warning from rustc nightly-2025-07-14

    warning: struct `Placeholder` is never constructed
      --> src/display.rs:63:16
       |
    63 |     pub struct Placeholder;
       |                ^^^^^^^^^^^
       |
       = note: `#[warn(dead_code)]` on by default

Author: dtolnay

src/display.rs

@@ -60,6 +60,7 @@ mod placeholder {
     use super::{AsDisplay, Sealed};
     use core::fmt::{self, Display};
 
+    #[allow(dead_code)]
     pub struct Placeholder;
 
     impl<'a> AsDisplay<'a> for Placeholder {