Extract value from nested tuple by given type

tuple_getter.rs

// https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=440c65898633c8dba89e0a036f049e95
use std::ops::Deref;
use std::marker::PhantomData;

#[repr(transparent)]
struct Getter<A, T>(T, PhantomData<A>);

impl<A, T, U> Deref for Getter<A, (T, U)> {
    type Target = Getter<A, U>;
    fn deref(&self) -> &Self::Target {
        unsafe { std::mem::transmute::<&U, &Getter<A, U>>(&self.0.1) }
    }
}

trait Has<T> {
    fn get(&self) -> &T;
}

impl<T, U> Has<T> for Getter<T, (T, U)> {
    fn get(&self) -> &T {
        &self.0.0
    }
}

fn getter<A, T>(tup: &T) -> &Getter<A, T> {
    unsafe { std::mem::transmute::<&T, &Getter<A, T>>(tup) }
}

fn main() {
    let tup = (1u32, ('2', ("3", (4i32, (5u8, (b"6", ()))))));
    dbg!(getter::<i32, _>(&tup).get());     // 4
    dbg!(getter::<&str, _>(&tup).get());    // "3"
    dbg!(getter::<u32, _>(&tup).get());     // 1
    // dbg!(getter::<i64, _>(&tup).get());     // compile error
}