[rust] References to traits in structs

ref_traits.rs

/// see https://stackoverflow.com/questions/26212397/references-to-traits-in-structs
#![allow(unused)]
use std::borrow::Borrow;
trait Type {
    fn type_to_string(&self) -> String;
}

struct BoolType {}

impl Type for BoolType {
    fn type_to_string(&self) -> String {
        String::from("BOOL")
    }
}

struct IntType {}

impl Type for IntType {
    fn type_to_string(&self) -> String {
        String::from("INT")
    }
}

struct TypeInstance {
    types: [Box<dyn Type + 'static>; 2],
}

impl TypeInstance {
    fn new() -> Self {
        Self {
            types: [Box::new(BoolType{}), Box::new(IntType{})],
        }
    }
    
    fn get_bool_instance(&self) ->  &dyn Type  {
        self.types[0].borrow()
    }
    
    fn get_int_instance(&self) ->  &dyn Type  {
        self.types[1].borrow()
    }
}



fn main() {
    let TYPE_INSTANCE: TypeInstance = TypeInstance::new();

    println!("{}", TYPE_INSTANCE.get_bool_instance().type_to_string());
    println!("{}", TYPE_INSTANCE.get_int_instance().type_to_string());
}