Error code E0057

An invalid number of arguments was given when calling a closure.

Erroneous code example:

#![allow(unused)]
fn main() {
let f = |x| x * 3;
let a = f();        // invalid, too few parameters
let b = f(4);       // this works!
let c = f(2, 3);    // invalid, too many parameters
}

When invoking closures or other implementations of the function traits Fn, FnMut or FnOnce using call notation, the number of parameters passed to the function must match its definition.

A generic function must be treated similarly:

#![allow(unused)]
fn main() {
fn foo<F: Fn()>(f: F) {
    f(); // this is valid, but f(3) would not work
}
}