A test of phantom types in Rust. A bit more cumbersome than Haskell, but definitely doable.

phantom.rs

use std::marker::PhantomData;
use std::convert::From;

// Define the empty temperature markers
#[derive(Debug, Copy, Clone)] struct C; 
#[derive(Debug, Copy, Clone)] struct F;

// Temperature Struct with Phantom Data
#[derive(Debug, Copy, Clone)]
struct Temp<T> {
    temp: f64,
    unit: PhantomData<T>,
}

impl<T> Temp<T> {
    fn new(temp: f64) -> Temp<T> {
        Temp { temp, unit: PhantomData }
    }
}

// Conversion from F to C
impl From<Temp<F>> for Temp<C> {
    // [°C] = ([°F] − 32) × ​5⁄9
    fn from(temp: Temp<F>) -> Self {
        let f = temp.temp;
        Temp::new((f - 32.0) * 5.0 / 9.0)
    }
}

// Conversion from C to F
impl From<Temp<C>> for Temp<F> {
    //[°F] = [°C] × ​9⁄5 + 32 
    fn from(temp: Temp<C>) -> Self {
        let c = temp.temp;
        Temp::new(c * 9.0 / 5.0 + 32.0)
    }
}

fn main() {
    let c: Temp<C> = Temp::new(20.0);
    let f: Temp<F> = c.into();
    
    println!("Testing conversion from 20°C to °F");
    println!("°C: {:?}", c);
    println!("°F: {:?}", f);
    
    let f: Temp<F> = Temp::new(-40.0);
    let c: Temp<C> = f.into();
    
    println!("Testing conversion from -40°F to °C");
    println!("°F: {:?}", f);
    println!("°C: {:?}", c);
}