Function tracing::stdlib::fmt::from_fn

pub fn from_fn<F>(f: F) -> FromFn<F>
where
    F: Fn(&mut Formatter<'_>) -> Result<(), Error>,

🔬This is a nightly-only experimental API. (debug_closure_helpers #117729)

Creates a type whose fmt::Debug and fmt::Display impls are provided with the function f.

Examples

#![feature(debug_closure_helpers)]
use std::fmt;

let value = 'a';
assert_eq!(format!("{}", value), "a");
assert_eq!(format!("{:?}", value), "'a'");

let wrapped = fmt::from_fn(|f| write!(f, "{value:?}"));
assert_eq!(format!("{}", wrapped), "'a'");
assert_eq!(format!("{:?}", wrapped), "'a'");