Shared via Rust Playground

playground.rs

// The error is that there's an unused generic G declared...
fn foo<G>() -> String {
    String::from("hi")
}

fn main() {
    println!("{}", foo());
    //             ^ but here is where the error message points to:
    // error: unable to infer enough type information about `_`; type annotations or generic parameter binding required [E0282]
}