Make 'end" of SimpleSpan nonzero

[purpl3F0x]

Would it be more appropriate for end filed of the SimpleSpan be non-zero, so something like:

pub struct SimpleSpan<T = usize>
    pub start: T,
    pub end: std::num::NonZero<T>,
}

By definition, on the docs, the end is exclusive, so (0,0) values should not be valid.
This will have the added benefit, of Option<SimpleSpan>, not requiring an extra byte.

(https://play.rust-lang.org/?gist=63b58e61f659c6613cf1bba8035def00)

[zesterer]

(0, 0) is a valid span because spans can be (and frequently are) zero-length. Consider the following:

let function_call = ident
    .then(arg.repeated().collect().map(|args, e| (args, e.span())
        .delimited_by(lparen, rparen));

function_call.parse("foo()");

What span should the arguments receive? It would not be correct to have the span select the parentheses, since they surround the arguments but are themselves not the arguments. The correct span is a zero-width one that fits between the parentheses.

[purpl3F0x]

I though this could be something like (4, 4), which is zero length also.
But your point is still valid, for other examples. Something similar "args" could be at the start of the string, let's say a C-like include for example, or a docstring