Update CHANGELOG

Author: CodaFi

CHANGELOG.md

@@ -5,9 +5,42 @@ _**Note:** This is in reverse chronological order, so newer entries are added to
 
 ## Swift 5.7
 
+* [SE-0353][]:
+
+  Protocols with primary associated types can now be used in existential types,
+  enabling same-type constraints on those associated types.
+
+  ```
+  let strings: any Collection<String> = [ "Hello" ]
+  ```
+
+  Note that language features requiring runtime support like dynamic casts
+  (`is`, `as?`, `as!`), as well as generic usages of parameterized existentials
+  in generic types (e.g. `Array<any Collection<Int>>`) involve additional
+  availability checks to use. Back-deploying usages in generic position can be
+  worked around with a generic type-erasing wrapper struct, which is now much
+  simpler to implement:
+
+  ```swift
+  struct AnyCollection<T> {
+    var wrapped: any Collection<T>
+  }
+
+  let arrayOfCollections: [AnyCollection<T>] = [ /**/ ]
+  ```
+  
 * [SE-0329][]:
   New types representing time and clocks were introduced. This includes a protocol `Clock` defining clocks which allow for defining a concept of now and a way to wake up after a given instant. Additionally a new protocol `InstantProtocol` for defining instants in time was added. Furthermore a new protocol `DurationProtocol` was added to define an elapsed duration between two given `InstantProtocol` types. Most commonly the `Clock` types for general use are the `SuspendingClock` and `ContinuousClock` which represent the most fundamental clocks for the system. The `SuspendingClock` type does not progress while the machine is suspended whereas the `ContinuousClock` progresses no matter the state of the machine. 
 
+* [SE-0309][]:
+
+  Protocols with associated types and `Self` requirements can now be used as the
+  types of values with the `any` keyword.
+
+  Protocol methods that return associated types can be called on an `any` type;
+  the result is type-erased to the associated type's upper bound, which is another
+  `any` type having the same constraints as the associated type. For example:
+
   ```swift
     func delayedHello() async throws {
       try await Task.sleep(until: .now + .milliseconds(123), clock: .continuous)