This adds improved support for map patterns. A new [Restriction]
class replaces the [TypeBasedStaticType.identity] properties and
allows not only for unique values as subtypes but also subsets of
values as subtypes. For map pattern the subsets are defined by
a [MapTypeIdentity] based on the type arguments of the map pattern,
its constant key values and whether it has a rest pattern.
Change-Id: I32b95f519cc161975af17ea82beacbc27ad5bbe1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/287464
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>
Johnni Winther
eaedc90684