This establishes the base functionality. A lot of follow-up work is
needed from here:
- Each trace should have an entry at the top of it pointing to the
thing that was made nullable.
- The source code links in traces don't include lengths, so we can't
highlight whole identifiers when the user clicks on a link.
- Description strings are currently generated by running toString() on
the individual nullability nodes and edges, resulting in long-winded
and useless descriptions.
Change-Id: Ibb370bae6bedc7a8c86092462785023002a48ac3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138481
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Paul Berry
a74253987b