Document getting source_locations

[computerquip-work]

I was struggling a bit getting reasonable error codes. I use the exception-based API for readability purposes. Most of these functions take a source_location parameter but it turns out that the location information is lost when the exception is thrown. For example a call to at() on a json::object will drop the information and instead have the call site of the internal function:

value const&
object::
at(string_view key, source_location const& loc) const&
{
    return try_at(key).value(loc);
}

try_at gets called and throws so loc being set in the result type doesn't matter.
Is there a decent way to avoid this short of wrapping everything?

[computerquip-work]

Welp, I'm wrong here. There's two source_location objects being stored, one in the ec and one in the location_ over in throw_location. I thought the macro in try_at conditionally threw if exceptions were enabled but I was obviously wrong. In order to get the correct throw location, seems a call to get_throw_location has to be made. I guess I learned a bit more about boost exceptions today. Sorry fro the clutter.

[grisumbras]

Sorry fro the clutter.

No problem. I should really document how to get the corresponding source_locations. The fact that you were confused by them highlights it. I'm reopening the issue and repurposing it for tracking documentation for dealing with source_locations.