rust struct with generics compile error

Question

I wrote following code in rust. version is 0.12.0-pre-nightly.

struct Sample<T> {
    x: T
}

impl<T> Sample<T> {
    pub fn new<T>(v: T) -> Sample<T> {
        Sample { x: v }
    }

    pub fn get<T>(&self) -> T {
        self.x
    }
}

fn main() {
    Sample::new(0i).get(); // expect int 0
}

and got compile error.

hoge.rs:11:9: 11:15 error: mismatched types: expected `T`, found `T` (expected type parameter, found type parameter)
hoge.rs:11         self.x

I cannot figure out by compiler message why sample program cannot be compiled. How can I fix it?

Francis Gagné · Accepted Answer · 2014-09-27 06:11:44Z

1

Don't put type parameters on your methods. They must use the one from the impl.

struct Sample<T> {
    x: T
}

impl<T> Sample<T> {
    pub fn new(v: T) -> Sample<T> {
        Sample { x: v }
    }

    pub fn get(&self) -> T {
        self.x
    }
}

fn main() {
    Sample::new(0i).get(); // expect int 0
}

P.S.: That code doesn't compile either because get tries to move x out of &self. You can change impl<T> to impl<T: Copy> if you want to use copyable types only, or change get to return a reference:

    pub fn get(&self) -> &T {
        &self.x
    }

answered Sep 27, 2014 at 6:11

Francis Gagné

66.7k13 gold badges201 silver badges172 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

rust struct with generics compile error

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related