Tests: Account for concurrency availability in attr_backDeploy.swift and move tests for @_backDeploy and @objc interaction to attr_objc.swift.

Author: tshortli

test/attr/attr_backDeploy.swift

@@ -55,7 +55,7 @@ final public class FinalTopLevelClass {
 }
 
 // OK: final function decls on an actor
-@available(macOS 11.0, *)
+@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
 public actor TopLevelActor {
   @available(macOS 11.0, *)
   @_backDeploy(macOS 12.0)
@@ -123,7 +123,7 @@ extension TopLevelStruct {}
 @_backDeploy(macOS 12.0) // expected-error {{'@_backDeploy' attribute cannot be applied to this declaration}}
 protocol CannotBackDeployProtocol {}
 
-@available(macOS 11.0, *)
+@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
 @_backDeploy(macOS 12.0) // expected-error {{'@_backDeploy' attribute cannot be applied to this declaration}}
 public actor CannotBackDeployActor {}
 
@@ -147,11 +147,6 @@ public class TopLevelClass2 {
   @_backDeploy(macOS 12.0) // expected-error {{'@_backDeploy' cannot be applied to a non-final instance method}}
   public func nonFinalMethod() {}
 
-  @available(macOS 11.0, *)
-  @_backDeploy(macOS 12.0)
-  @objc // expected-error {{'@objc' cannot be applied to a back deployed instance method}}
-  final public func objcMethod() {}
-
   @_backDeploy(macOS 12.0) // expected-error {{'@_backDeploy' cannot be applied to a non-final class method}}
   public class func nonFinalClassMethod() {}
 }

test/attr/attr_objc.swift

@@ -2655,3 +2655,12 @@ class SR12801 {
   subscript<T>(foo : [T]) -> Int { return 0 }
   // access-note-adjust{{@objc}} expected-error@-1 {{subscript cannot be marked @objc because it has generic parameters}}
 }
+
+// @_backDeploy
+
+public class BackDeployClass {
+  @available(macOS 11.0, *)
+  @_backDeploy(macOS 12.0)
+  @objc // expected-error {{'@objc' cannot be applied to a back deployed instance method}}
+  final public func objcMethod() {}
+}