Macro delegate_renderer 

macro_rules! delegate_renderer {
    ($self:ident . $inner:ident) => { ... };
}

Macro to delegate all Renderer methods to an inner renderer.

Usage:

struct MyRenderer { inner: PostgresRenderer }
impl Renderer for MyRenderer {
    fn render_cast(&self, ...) { /* custom */ }
    delegate_renderer!(self.inner);
}