Initiial source ID and location

[eaglgenes101]

In the method to create a report builder, there are two arguments corresponding to a source ID and a location. From reading the source code, these correspond to a location field inside the report builder struct, which is only ever used in

ariadne/src/write.rs

Line 137 in e3cb394

let location = if src_id == self.location.0.borrow() {

and following lines for determining a source location in certain cases. Am I missing something, or am I correct in thinking that this initial location could (and for ease of end usage, should) be made optional?

[bestouff]

Also the docs aren't clear about what's its use, and the multifiles example makes it look like it's redundant.

[zesterer]

I think I'm going to remove this in favour of a 'blessed' primary label that gets used as the canonical error location. I do want to keep this notion of there being a canonical single location for the error though, because this would allow for reporting short form errors in a manner similar to Rust's --message-format=short.

[bestouff]

That sounds perfect.
For now my code scans the different labels and finds the Primary one, then uses this as the location for Report::build().