Code shared from the Rust Playground

playground.rs

use std::marker::PhantomData;

struct Normal;
struct Auction;
struct Stop;

enum Mode {
    Normal(Normal),
    Auction(Auction),
    Stop(Stop),
}

struct MatcherState {
}

struct Service {
    mode: Mode,
    state: MatcherState,
}

impl Service {
    fn place_order(&mut self) {
        match self.mode {
            Mode::Normal(Normal) => Matcher::<Normal>::new(&mut self.state).place_order(),
            Mode::Auction(Auction) => Matcher::<Auction>::new(&mut self.state).place_order(),
            Mode::Stop(Stop) => Matcher::<Stop>::new(&mut self.state).place_order(),
        }
    }
    
    fn cancel_order(&mut self) {}
    
    // ...
}

struct Matcher<T> {
    _p: PhantomData<T>,
}

impl<T> Matcher<T> {
    fn new(state: &mut MatcherState) -> Matcher<T> {
        Matcher { _p: PhantomData }
    }
}

impl Matcher<Normal> {
    fn place_order(&mut self) {
        
    }
    
    fn cancel_order(&mut self) {
        
    }
}

impl Matcher<Auction> {
    fn place_order(&mut self) {
        
    }
    
    fn cancel_order(&mut self) {
        
    }
}

impl Matcher<Stop> {
    fn place_order(&mut self) {
        
    }
    
    fn cancel_order(&mut self) {
        
    }
}