Consider impl <T, R: Into<T>> IntoRequest<T> for R

[stevenroose]

Feature Request

Tonic's client functions take IntoRequest<T> for the request type. But if I have a type R that implements Into<T>, I can't pass my_r.into() into the function because the type system won't figure out that I want the .into() for T.

If we'd have a generic implementation as below, we could pass an R object into the client method.

impl <R, T: From<R>> IntoRequest<T> for R {
    fn into_request(self) -> Request<T> {
        T::from(self).into_request()
    }
}

Motivation

Simplifying calling client functions with custom structs that Into the protobuf requests. I think this is a common pattern. The protobuf messages use only the raw types, so often clients have structs with business logic types and then conversion Into and TryFrom implementations between business-logic structs and protobuf structs.

[stevenroose]

Just realized that probably because From<T> is implemented for T, this is impossible, because then we couldn't implement IntoRequest anymore by the original type?