Type Alias InputFn 

pub type InputFn<'a> = Option<&'a mut dyn FnMut() -> Option<String>>;

A run’s source of input: one line per call, with no line terminator, and None once the input has ended.

None in place of the closure is a run the host attached no input to at all, which is a different thing from a source that has run out: the first is a wiring mistake in the embedding, the second is the program asking for more than it was given, and the two say so differently.

Aliased Type

pub enum InputFn<'a> {
    None,
    Some(&'a mut dyn FnMut() -> Option<String>),
}

Variants

None

No value.

Some(&'a mut dyn FnMut() -> Option<String>)

Some value of type T.