Merge pull request #42361 from AnthonyLatsis/5.7-changelog-dynamic-lookup-unbound-ref

🍒 [5.7] Add CHANGELOG entry for #41849 and #42332

Author: AnthonyLatsis

CHANGELOG.md

@@ -5,6 +5,22 @@ _**Note:** This is in reverse chronological order, so newer entries are added to
 
 ## Swift 5.7
 
+* References to `optional` methods on a protocol metatype, as well as references to dynamically looked up methods on the `AnyObject` metatype are now supported. These references always have the type of a function that accepts a single argument and returns an optional value of function type:
+
+  ```swift
+  class Object {
+    @objc func getTag() -> Int
+  }
+
+  @objc protocol P {
+    @objc optional func didUpdateObject(withTag tag: Int)
+  }
+
+  let getTag: (AnyObject) -> (() -> Int)? = AnyObject.getTag
+
+  let didUpdateObject: (any P) -> ((Int) -> Void)? = P.didUpdateObject
+  ```
+
 * [SE-0352][]:
 
   It's now possible to call a generic function with a value of protocol type
@@ -32,7 +48,7 @@ _**Note:** This is in reverse chronological order, so newer entries are added to
   It's now possible to use a default value expression with a generic parameter type
   to default the argument and its type:
 
-  ```
+  ```swift
   func compute<C: Collection>(_ values: C = [0, 1, 2]) {
     ...
   }

test/Interpreter/dynamic_lookup.swift

@@ -5,6 +5,10 @@
 
 import Foundation
 
+@objc protocol P {
+  @objc optional func e()
+}
+
 class X {
   init() {}
 
@@ -15,11 +19,15 @@ class X {
     return 17
   }
 }
+extension X: P {
+  @objc func e() { print("X.e()") }
+}
 
 class Y { 
   init() {}
   @objc class func g() { print("Y.g()") }
 }
+extension Y: P {}
 
 class Z {
    init() {}
@@ -44,7 +52,16 @@ func test_dynamic_lookup_f_unbound(_ obj: AnyObject) {
   if of != nil {
     of!()
   } else {
-    print("Object does not respond to the selector \"f\".\n", terminator: "")
+    print("\(type(of: obj)) does not respond to the selector \"f\"")
+  }
+}
+
+func test_dynamic_lookup_e_unbound(_ obj: AnyObject) {
+  var oe = AnyObject.e(obj)
+  if oe != nil {
+    oe!()
+  } else {
+    print("\(type(of: obj)) does not respond to the selector \"e\"")
   }
 }
 
@@ -77,11 +94,20 @@ test_dynamic_lookup_f(Z())
 print(type(of: AnyObject.f))
 // CHECK-NEXT: X.f()
 test_dynamic_lookup_f_unbound(X())
-// CHECK-NEXT: Object does not respond to the selector "f"
+// CHECK-NEXT: Y does not respond to the selector "f"
 test_dynamic_lookup_f_unbound(Y())
 // CHECK-NEXT: Z.f()
 test_dynamic_lookup_f_unbound(Z())
 
+// CHECK-NEXT: (AnyObject) -> Optional<() -> ()>
+print(type(of: AnyObject.e))
+// CHECK-NEXT: X.e()
+test_dynamic_lookup_e_unbound(X())
+// CHECK-NEXT: Y does not respond to the selector "e"
+test_dynamic_lookup_e_unbound(Y())
+// CHECK-NEXT: Z does not respond to the selector "e"
+test_dynamic_lookup_e_unbound(Z())
+
 // CHECK: Class does not respond to the selector "g"
 test_dynamic_lookup_g(X())
 // CHECK: Y.g()