Is it possible to have a constructor function in a trait?

Question

I\'m trying to find examples for constructor functions in traits, but haven\'t had much luck. Is this a idiomatic thing to do in Rust?

Answer 1

You need to use the Self type. In trait declarations, Self refers to the type that implements a trait. In your case, the trait declaration should look as follows:

trait A {
    fn new() -> Self; // Self stands for any type implementing A
}

Your original version is subtly different because it will return a trait object, not a value of the implementor type.