tree 06c18fc84ba263f6bbbb9b89278cc49eb39ed5c9
parent 6a90c21992e659de8f6c171d7ab6eaf7f4f9eba4
author Paul Berry <paulberry@google.com> 1676385756 +0000
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> 1676385756 +0000

Flow analysis: implement type promotion for record patterns.

For each subpattern of a record pattern, we define its "demonstrated
type" to be the type that the matched value has been promoted to if
the subpattern match succeeds.  At the conclusion of visiting a record
pattern, we promote the whole record pattern's matched value to a
record type formed by combining together the demonstrated types of the
subpatterns.  So, for example, the pattern `(int _, String _)`
promotes the matched value to `(int, String)`.

This change contains a lot of specific tests, to make sure the
demonstrated type of each kind of pattern behaves as expected; but the
actual machinery is general, since it just takes advantage of the type
promotion performed by the subpatterns.

Bug: https://github.com/dart-lang/sdk/issues/50419
Change-Id: Ie4da81964b5ade657c23a598ee18982b793fb4ac
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/282806
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>