param-attrs.md

param_attrs

The tracking issue for this feature is: #60406

Allow attributes in formal function parameter position so external tools and compiler internals can take advantage of the additional information that the parameters provide.

Enables finer conditional compilation with #[cfg(..)] and linting control of variables. Moreover, opens the path to richer DSLs created by users.

---

Example:

#![feature(param_attrs)]

fn len(
  #[cfg(windows)] slice: &[u16],
  #[cfg(not(windows))] slice: &[u8],
) -> usize
{
  slice.len()
}