E4017

Method of type is ambiguous, it may come from multiple traits.

Erroneous Example

struct S { v : Int } derive(Show)

trait Tee { to_string(Self) -> String }

impl Tee for S with to_string(_self) { "Tee" }

let s : S = { v: 3 }
let t = s.to_string()

The example above tries to call the method to_string on a type S, but the method name comes from both Show and Tee traits, giving the following error on line 8:

Method to_string of type S is ambiguous, it may come from trait Tee or Show

Suggestion

Disambiguate the method by specifying the trait it comes from:

struct S { v : Int } derive(Show)

trait Tee { to_string(Self) -> String }

impl Tee for S with to_string(_self) { "Tee" }

let s : S = { v: 3 }
let t = Tee::to_string(s)