SharedType and its subtypes now all declare one recursive type
variable Type with the bound SharedType<Type>. It allows to treate
SharedType and its subtypes as an abstract familty of types that has a
specific structure.
More specifically, the type variables Type and TypeSchema in the
abstract classes for shared algorithms between the Analyzer and the
CFE can now be defined recursively as extending SharedType<Type> and
SharedType<TypeSchema>, giving both types and type schemas the
structure of the family of types with the root at SharedType.
One of the benefits for that is that some abstract members become
unnecessary. For example, a type or type schema can now be tested for
having the shape of the type 'dynamic' with a direct is-check,
comparing them, correspondingly, with SharedType<Type> and
SharedType<TypeSchema>.
More importantly, having the family of recursive types lays the
foundation for further work on sharing the type structure between the
Analyzer and the CFE.
Change-Id: I67904f878668c035702092e8c21d3ce66f5ca469
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/378700
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Chloe Stefantsova <cstefantsova@google.com>
Chloe Stefantsova
cf0e927a43