Auto merge of #36585 - jonathandturner:misc_error_touchups, r=nrc

Add the ability to merge spans to codemap

This PR adds the ability to merge Spans.  To do so, it builds on the Codemap's ability to verify the locations of spans, namely that following can be verified:

* the expn_id of both spans much match
* the lhs span needs to end on the same line the rhs span begins
* the lhs span must start at or before the rhs span

If all of these are met, a new span is returned that is min(lo), max(hi) of the two spans.

This PR also removes an older Span merge, as this new functionality subsumes it.

r? @nrc

0 files changed, 0 insertions, 0 deletions