Rust does not compare function argument types when determining which trait's implementation to use

wow.rs

/// Won't compile:
///
///    $ rustc wow.rs 
///    error[E0034]: multiple applicable items in scope
///      --> wow.rs:33:9
///       |
///    33 |     foo.wow("TSecond is str");
///       |         ^^^ multiple `wow` found
///       |
///    note: candidate #1 is defined in an impl of the trait `TFirst` for the type `Foo`
///      --> wow.rs:13:5
///       |
///    13 |     fn wow(&self, extra: i64) {
///       |     ^^^^^^^^^^^^^^^^^^^^^^^^^
///    note: candidate #2 is defined in an impl of the trait `TSecond` for the type `Foo`
///      --> wow.rs:22:5
///       |
///    22 |     fn wow(&self, extra: &str) {
///       |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
///
///    error: aborting due to previous error
///
///    For more information about this error, try `rustc --explain E0034`.



#[derive(Debug)]
struct Foo{x:u64}

trait TFirst {
    fn wow(&self, i64);
}

trait TSecond {
    fn wow(&self, &str);
}

impl TFirst for Foo {
    fn wow(&self, extra: i64) {
        for i in 0..self.x {
            println!("TFirst wow {} of {}", i+1, self.x);
        }
        println!("-- extra: {}", extra);
    }
}

impl TSecond for Foo {
    fn wow(&self, extra: &str) {
        for i in 0..self.x {
            println!("TSecond wow {} of {}", i+1, self.x);
        }
        println!("-- extra: {}", extra);
    }
}

fn main() {
    let foo = Foo{x:3};
    println!("{:?}", foo);
    foo.wow("TSecond is str");
}