[Type checker] Check for recursion when evaluating @objc on a property.

Fixes crash from rdar://problem/33093935.

Author: DougGregor

lib/Sema/TypeCheckDeclObjC.cpp

@@ -759,6 +759,11 @@ bool swift::isRepresentableInObjC(const VarDecl *VD, ObjCReason Reason) {
   if (!VD->hasInterfaceType()) {
     VD->getASTContext().getLazyResolver()->resolveDeclSignature(
                                               const_cast<VarDecl *>(VD));
+    if (!VD->hasInterfaceType()) {
+      VD->diagnose(diag::recursive_type_reference, VD->getDescriptiveKind(),
+                   VD->getName());
+      return false;
+    }
   }
 
   Type T = VD->getDeclContext()->mapTypeIntoContext(VD->getInterfaceType());

validation-test/compiler_crashers_2_fixed/0177-rdar-33093935.swift

@@ -0,0 +1,14 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -primary-file %s %S/Inputs/0177-rdar-33093935-other.swift -verify
+
+// REQUIRES: objc_interop
+
+import Foundation
+
+extension A {
+  static func superclass() -> AnyObject? { return nil }
+  @objc var name: String { return "hi" }
+}
+
+class B: A {
+  @objc var foo = superclass()?.name // expected-error{{property 'foo' references itself}}
+}

validation-test/compiler_crashers_2_fixed/Inputs/0177-rdar-33093935-other.swift

@@ -0,0 +1,3 @@
+import Foundation
+
+class A: NSObject { }