This doesn't comprehensively cover everything we should test around
pattern variable scopes, but I wanted to cover most of the tricky
behavior around variables in cases that share a body, along with some
other edge cases that I thought of while speccing that out.
Change-Id: I64fff7b4a9a30b00801fbf37b52f07799ef0fd35
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/268370
Commit-Queue: Bob Nystrom <rnystrom@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>
Reviewed-by: Kallen Tu <kallentu@google.com>