stdlib: Use the original === and !== operators on embedded

It seems that the restriction preventing these from working was
lifted.

The behavioral difference is that in Swift 5 mode, we don't
actually open AnyObject like this, so the old operator could
not be used with class-bound existentials.

I added a trivial test case just to ensure that calls to ===
type check correctly in both language modes.

Fixes rdar://156095800.

Author: slavapestov

stdlib/public/core/Equatable.swift

@@ -271,7 +271,7 @@ public func === (lhs: AnyObject?, rhs: AnyObject?) -> Bool {
 #else
 @inlinable // trivial-implementation
 @safe
-public func ===<T: AnyObject, U: AnyObject>(lhs: T?, rhs: U?) -> Bool {
+public func === (lhs: AnyObject?, rhs: AnyObject?) -> Bool {
   switch (lhs, rhs) {
   case let (l?, r?):
     return Builtin.bridgeToRawPointer(l) == Builtin.bridgeToRawPointer(r)
@@ -293,14 +293,7 @@ public func ===<T: AnyObject, U: AnyObject>(lhs: T?, rhs: U?) -> Bool {
 /// - Parameters:
 ///   - lhs: A reference to compare.
 ///   - rhs: Another reference to compare.
-#if !$Embedded
 @inlinable // trivial-implementation
 public func !== (lhs: AnyObject?, rhs: AnyObject?) -> Bool {
   return !(lhs === rhs)
 }
-#else
-@inlinable // trivial-implementation
-public func !==<T: AnyObject, U: AnyObject>(lhs: T, rhs: U) -> Bool {
-  return !(lhs === rhs)
-}
-#endif

test/embedded/anyobject.swift

@@ -0,0 +1,36 @@
+// RUN: %target-run-simple-swift(-enable-experimental-feature Embedded -parse-as-library -wmo -swift-version 5) | %FileCheck %s
+// RUN: %target-run-simple-swift(-enable-experimental-feature Embedded -parse-as-library -wmo -O -swift-version 5) | %FileCheck %s
+// RUN: %target-run-simple-swift(-enable-experimental-feature Embedded -parse-as-library -wmo -Osize -swift-version 5) | %FileCheck %s
+
+// RUN: %target-run-simple-swift(-enable-experimental-feature Embedded -parse-as-library -wmo -swift-version 6) | %FileCheck %s
+// RUN: %target-run-simple-swift(-enable-experimental-feature Embedded -parse-as-library -wmo -O -swift-version 6) | %FileCheck %s
+// RUN: %target-run-simple-swift(-enable-experimental-feature Embedded -parse-as-library -wmo -Osize -swift-version 6) | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+// REQUIRES: executable_test
+// REQUIRES: optimized_stdlib
+// REQUIRES: swift_feature_Embedded
+
+protocol P: AnyObject {}
+
+class C: P {}
+
+@main
+struct Main {
+    static func main() {
+        let p1: any P = C()
+        let p2: any P = C()
+        let p3 = p1
+
+        // CHECK: false
+        print(p1 === p2)
+        print(p2 === p1)
+        // CHECK: true
+        print(p1 === p3)
+        print(p3 === p1)
+        // CHECK: false
+        print(p2 === p3)
+        print(p3 === p2)
+   }
+}
+