Error code E0790

You need to specify a specific implementation of the trait in order to call the method.

Erroneous code example:

#![allow(unused)]
fn main() {
trait Generator {
    fn create() -> u32;
}

struct Impl;

impl Generator for Impl {
    fn create() -> u32 { 1 }
}

struct AnotherImpl;

impl Generator for AnotherImpl {
    fn create() -> u32 { 2 }
}

let cont: u32 = Generator::create();
// error, impossible to choose one of Generator trait implementation
// Should it be Impl or AnotherImpl, maybe something else?
}

This error can be solved by adding type annotations that provide the missing information to the compiler. In this case, the solution is to use a concrete type:

#![allow(unused)]
fn main() {
trait Generator {
    fn create() -> u32;
}

struct AnotherImpl;

impl Generator for AnotherImpl {
    fn create() -> u32 { 2 }
}

let gen1 = AnotherImpl::create();

// if there are multiple methods with same name (different traits)
let gen2 = <AnotherImpl as Generator>::create();
}