Type Alias DeferredGeneration 

pub type DeferredGeneration<'s, SI> = Box<dyn FnOnce(&mut SI, &mut String) -> SyntaxInterpreterResult<'s, (), <SI as SyntaxInterpreter>::Error> + 's>;

It’s just a simple closure that provides (interpreter, out_buffer) in its arguments and allows borrowing the outside context.

Aliased Type

pub struct DeferredGeneration<'s, SI>(/* private fields */);