Allow 'Any' as an IBAction's sender and an IBOutlet's type. (#4320)

With id-as-Any, /existing/ IBAction methods that have unconstrained
sender parameters are being imported as taking 'Any?', and those
methods then can't be overridden in Swift.

We still don't allow arbitrary bridgeable types for IBActions and
IBOutlets. This makes enough sense for value types, but might get us
into trouble with swift_newtype at some point.

rdar://problem/27853737

Author: jrose-apple

lib/Sema/TypeCheckAttr.cpp

@@ -343,7 +343,7 @@ void AttributeEarlyChecker::visitSILStoredAttr(SILStoredAttr *attr) {
 
 static Optional<Diag<bool,Type>>
 isAcceptableOutletType(Type type, bool &isArray, TypeChecker &TC) {
-  if (type->isObjCExistentialType())
+  if (type->isObjCExistentialType() || type->isAny())
     return None; // @objc existential types are okay
 
   auto nominal = type->getAnyNominal();
@@ -800,8 +800,8 @@ static bool checkObjectOrOptionalObjectType(TypeChecker &TC, Decl *D,
         .highlight(param->getSourceRange());
       return true;
     }
-  } else if (ty->isObjCExistentialType()) {
-    // @objc existential types are okay
+  } else if (ty->isObjCExistentialType() || ty->isAny()) {
+    // @objc existential types are okay, as is Any.
     // Nothing to do.
   } else {
     // No other types are permitted.

test/attr/attr_ibaction.swift

@@ -63,6 +63,11 @@ protocol CP2 : class { }
   @IBAction func action5(_: AnyObject?) {}
   @IBAction func action6(_: AnyObject!) {}
 
+  // Any
+  @IBAction func action4a(_: Any) {}
+  @IBAction func action5a(_: Any?) {}
+  @IBAction func action6a(_: Any!) {}
+
   // Protocol types
   @IBAction func action7(_: P1) {} // expected-error{{argument to @IBAction method cannot have non-object type 'P1'}}
   // expected-error@-1{{method cannot be marked @IBAction because the type of the parameter cannot be represented in Objective-C}}

test/attr/attr_iboutlet.swift

@@ -64,6 +64,10 @@ class NonObjC {}
   @IBOutlet var outlet5: AnyObject?
   @IBOutlet var outlet6: AnyObject!
 
+  // Any
+  @IBOutlet var outlet5a: Any?
+  @IBOutlet var outlet6a: Any!
+
   // Protocol types
   @IBOutlet var outlet7: P1 // expected-error{{@IBOutlet property cannot have non-'@objc' protocol type 'P1'}} {{3-13=}}
   @IBOutlet var outlet8: CP1 // expected-error{{@IBOutlet property cannot have non-'@objc' protocol type 'CP1'}} {{3-13=}}