pub trait Render {
type Error;
fn render_into<W: Write>(&self, w: &mut W) -> Result<(), Self::Error>;
fn render(&self) -> Result<String, Self::Error> { ... }
}
pub trait Render {
type Error;
fn render_into<W: Write>(&self, w: &mut W) -> Result<(), Self::Error>;
fn render(&self) -> Result<String, Self::Error> { ... }
}