rust/src/librustc_error_codes/error_codes/E0283.md

This error occurs when the compiler doesn't have enough information to unambiguously choose an implementation.

For 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 }
}

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

To resolve this error use the concrete type:

trait Generator {
    fn create() -> u32;
}

struct AnotherImpl;

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

fn main() {
    let gen1 = AnotherImpl::create();

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