Analog of delimited_by with better error generation

[Hedgehogo]

I would like to have an analog of delimited_by, which would allow to pass to the error that occurred when the closing parser worked, information about how the opening parser worked, most often span, the dumbest way to do it -
inner.xxx(just(“(”“), |span| just(”“)”).map_err(|e: Error| Error::new(Expected::TupleClose(OpenBracket::new(span.clone())), e.found(), e.span()). But clearly there is a more elegant solution using the abstractions we already have.

[zesterer]

So this actually existed in 0.9: Error had a dedicated method for unclosed delimiters and the nested_delimiters recovery strategy would make use of it.

We could do exactly the same thing in 1.0: perhaps if this is something you'd be happy with, we can go right ahead and just implement that. My feeling is that there might be space to add something that allows for more fine-grained control over the final error though, perhaps via the labelling system, allowing the unclosed delimiter to become an extra annotation on top of the existing error (i.e: a new method that sits alongside LabelError::in_context).

Interested to know your thoughts!