Rust oddness: integer literal references?

A more formal description of this behavior: Rust does temporary lifetime extension: https://doc.rust-lang.org/stable/reference/destructors.html#...

  let x = &5;

  // x is still valid here because the 5 is no longer a temporary but lives for the rest of the block

As well as constant promotion, not discussed in the post but similar! https://doc.rust-lang.org/stable/reference/destructors.html?...

  let x: &'static i32 = &5;

(this was originally called "rvalue static promotion" but Rust has since moved away from the rvalue/lvalue terminology since that time)