Is using `ref` in a function argument the same as automatically taking a reference?

Question

Rust tutorials often advocate passing an argument by reference:

fn my_func(x: &Something)

This makes it necessary to explicitly take a reference of the value at the call site:

my_func(&my_value).

It is possible to use the ref keyword usually used in pattern matching:

fn my_func(ref x: Something)

I can call this by doing

my_func(my_value)

Memory-wise, does this work like I expect or does it copy my_value on the stack before calling my_func and then get a reference to the copy?

Answer 1

The value is copied, and the copy is then referenced.

fn f(ref mut x: i32) {
    *x = 12;
}

fn main() {
    let mut x = 42;
    f(x);
    println!("{}", x);
}

Output: 42