# Error code E0790

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

Erroneous code example:

ⓘ

    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?

Run

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:

    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();

Run

Back to list of error codes