The tracking issue for this feature is: #34511

The impl_trait_in_bindings feature gate lets you use impl Trait syntax in let, static, and const bindings.

A simple example is:

#![feature(impl_trait_in_bindings)]

use std::fmt::Debug;

fn main() {
    let a: impl Debug + Clone = 42;
    let b = a.clone();
    println!("{:?}", b); // prints `42`
}

Note however that because the types of a and b are opaque in the above example, calling inherent methods or methods outside of the specified traits (e.g., a.abs() or b.abs()) is not allowed, and yields an error.