Interface dispatch now unboxes a receiver it has matched by key with one
load and no reference count change, and keeps its checked fallback out of
line so the key tests inline at each call site. A loop over an array of
interface values lends each element to a dispatch whose implementing
methods cannot release it; the fallback, which can run any code, takes
its own reference to the receiver.
Arrays whose elements are class-backed interface values are native arrays
of the element capsules, so iteration, indexing and most array methods no
longer go through the checked-dynamic array, and method calls receive a
receiver they can dispatch. Methods without a native form for these
elements run on the array's live dynamic view.
A read of an interface property signature has the property's static type
and reads the field of an implementing class directly. Accessors, object
literals and JavaScript classes keep the checked property read.
Chris Tate