* Add special handling for String concatenations so the first string
gets mapped correctly and work better in sound null safety.
* Update variable assignments to more consistently point to helpful
locations, specifically when lowered from a prefix increment like
`++x`.
* Run the sourcemap and stacktrace test suites with sound null safety.
Previously these suites were running with unsound null safety so more
operations were wrapped in function calls to check for null. Those calls
allowed for mode step or break points that hid some of the issues
addressed in this change.
Issue: https://github.com/dart-lang/sdk/issues/55692
Change-Id: Ibd887c8da64e72ab84c0698dd49b845abfaedbb8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/366025
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>
Nicholas Shahan
1a0dd104d4