Rust's Deref coercion

Let me add explanation later 🙃

use std::ops::Deref;

#[derive(Debug)] 
struct Test {
   hi: String
}

impl Deref for Test {
    type Target = String;
    
    fn deref(&self) -> &Self::Target {
        &self.hi
    }
}

fn extract<T>(test: T) 
where
    T: Deref<Target=String> 
{
    // Deref coercion happens here
    let unwrapped: &String = &test; 
    println!("{:?}", unwrapped);
}

fn main() {
   let test = Test { 
       hi: "hello".to_string() 
   };
   
   extract(test); 
}