Clarify usage of `[NullAllowed]` in our bindings (#5417)

First part to fix https://github.com/xamarin/xamarin-macios/issues/5416 We currently allow the `[NullAllowed]` attribute anywhere an attribute can be used on metadata (i.e. no `AttributeUsage` is used). However the generator only process the attribute in some specific cases, *silently* ignoring others. This leads to situations such as ```csharp [NullAllowed, Export ("setInputHandler:")] void SetInputHandler (AUInputHandler handler); ``` where a `null` argument will throw an `ArgumentNullException` because `[NullAllowed]` does not mean anything on a method declaration. To avoid such confusion `[NullAllowed]` should be added on each parameter (even if all of them requires it) and if a `null` return value is possible then use `[return: NullAllowed]`. This PR allows XI/XM bindings to be built, without error, when this patch is applied. ```diff diff --git a/src/generator-attributes.cs b/src/generator-attributes.cs index 965d8469..77162253 100644 --- a/src/generator-attributes.cs +++ b/src/generator-attributes.cs @@ -250,6 +250,7 @@ public class IsThreadStaticAttribute : Attribute { // When applied to a member, generates the member as static // and passes IntPtr.Zero or null if the parameter is null +[AttributeUsage (AttributeTargets.Property | AttributeTargets.ReturnValue | AttributeTargets.Parameter)] public class NullAllowedAttribute : Attribute { public NullAllowedAttribute () {} } ``` Note that it's unlikely we'll apply this patch _as-is_ to avoid breaking existing projects. A better approach (in a future PR) is to have the generator (instead of the C# compiler) issue a warning (instead of an error) when a `NullAllowed` is ignored.
2019-01-16 09:42:45 -05:00 · 2019-01-16 09:42:45 -05:00 · 8757f36ca5
--- a/src/appkit.cs
+++ b/src/appkit.cs
@ -608,7 +608,8 @@ namespace AppKit {
 		NSMenu MainMenu { get; set; }
 	
 		[Export ("helpMenu", ArgumentSemantic.Retain)]
-		NSMenu HelpMenu { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSMenu HelpMenu { get; set; }
 	
 		[Export ("applicationIconImage", ArgumentSemantic.Retain)]
 		NSImage ApplicationIconImage { get; set; }
@ -1116,7 +1117,8 @@ namespace AppKit {
 		NSObject [] SortDescriptors { get; set; }

 		[Export ("filterPredicate", ArgumentSemantic.Retain)]
-		NSPredicate FilterPredicate { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSPredicate FilterPredicate { get; set; }

 		[Export ("clearsFilterPredicateOnInsertion")]
 		bool ClearsFilterPredicateOnInsertion { get; set; }
@ -5511,7 +5513,8 @@ namespace AppKit {
 		void ShouldCloseWindowController (NSWindowController windowController, NSObject delegateObject, Selector shouldCloseSelector, IntPtr contextInfo);

 		[Export ("displayName")]
-		string DisplayName { get; [NullAllowed] set; }
+		[NullAllowed]
+		string DisplayName { get; set; }

 		[Export ("windowForSheet")]
 		NSWindow WindowForSheet { get; }
@ -8117,7 +8120,8 @@ namespace AppKit {
 		NSMenu Menu { get; set; }

 		[Export ("submenu", ArgumentSemantic.Retain)]
-		NSMenu Submenu { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSMenu Submenu { get; set; }

 		[Export ("title")]
 		string Title { get; set; }
@ -10040,7 +10044,8 @@ namespace AppKit {

 		//Detected properties
 		[Export ("image", ArgumentSemantic.Retain)]
-		NSImage Image { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSImage Image { get; set; }

 		[Export ("imageAlignment")]
 		NSImageAlignment ImageAlignment { get; set; }
@ -12738,7 +12743,7 @@ namespace AppKit {
 	interface NSResponder_NSTouchBarProvider : INSTouchBarProvider
 	{
 		[Mac (10, 12, 2)]
-		[NullAllowed, Export ("touchBar")]
+		[Export ("touchBar")]
 		NSTouchBar GetTouchBar ();

 		[Mac (10, 12, 2)]
@ -12746,7 +12751,7 @@ namespace AppKit {
 		void SetTouchBar ([NullAllowed]NSTouchBar bar);

 		[Mac (10, 12, 2)]
-		[NullAllowed, Export ("makeTouchBar")]
+		[Export ("makeTouchBar")]
 		NSTouchBar MakeTouchBar ();
 	}

@ -14808,7 +14813,8 @@ namespace AppKit {

 		[Availability (Deprecated = Platform.Mac_10_10, Message = "Soft-deprecation, forwards message to button, but will be gone in the future.")]
 		[Export ("view")]
-		NSView View { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSView View { get; set; }

 		[Mac (10,10)]
 		[Export ("button", ArgumentSemantic.Retain)]
@ -20490,7 +20496,8 @@ namespace AppKit {
 		void MenuChanged (NSMenu  menu);
 	
 		[Export ("windowController")]
-		NSObject WindowController { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSObject WindowController { get; set; }
 	
 		[Export ("isSheet")]
 		bool IsSheet { get; }
@ -20555,7 +20562,8 @@ namespace AppKit {
 		NSSelectionDirection KeyViewSelectionDirection ();
 	
 		[Export ("defaultButtonCell")]
-		NSButtonCell DefaultButtonCell { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSButtonCell DefaultButtonCell { get; set; }
 	
 		[Export ("disableKeyEquivalentForDefaultButtonCell")]
 		void DisableKeyEquivalentForDefaultButtonCell ();
@ -25763,7 +25771,7 @@ namespace AppKit {
 	interface NSView_NSCandidateListTouchBarItem
 	{
 		[Mac (10, 12, 2)]
-		[NullAllowed, Export ("candidateListTouchBarItem")]
+		[Export ("candidateListTouchBarItem")]
 		NSCandidateListTouchBarItem GetCandidateListTouchBarItem (); 
 	}

--- a/src/audiounit.cs
+++ b/src/audiounit.cs
@ -311,11 +311,11 @@ namespace AudioUnit {
 		[Export ("setOutputEnabled:")]
 		bool SetOutputEnabled (bool enabled);
 		
-		[NullAllowed, Export ("inputHandler", ArgumentSemantic.Copy)]
+		[Export ("inputHandler", ArgumentSemantic.Copy)]
 		AUInputHandler GetInputHandler ();

-		[NullAllowed, Export ("setInputHandler:")]
-		void SetInputHandler (AUInputHandler handler);
+		[Export ("setInputHandler:")]
+		void SetInputHandler ([NullAllowed] AUInputHandler handler);

 		[Export ("startHardwareAndReturnError:")]
 		bool StartHardware ([NullAllowed] out NSError outError);
@ -323,11 +323,11 @@ namespace AudioUnit {
 		[Export ("stopHardware")]
 		void StopHardware ();

-		[NullAllowed, Export ("outputProvider", ArgumentSemantic.Copy)]
+		[Export ("outputProvider", ArgumentSemantic.Copy)]
 		AURenderPullInputBlock GetOutputProvider ();

-		[NullAllowed, Export ("setOutputProvider:")]
-		void SetOutputProvider (AURenderPullInputBlock provider);
+		[Export ("setOutputProvider:")]
+		void SetOutputProvider ([NullAllowed] AURenderPullInputBlock provider);

 		// the following are properties but we cannot have properties in Categories.
 		[Mac (10, 13), NoWatch, NoiOS, NoTV]
--- a/src/foundation.cs
+++ b/src/foundation.cs
@ -13226,7 +13226,8 @@ namespace Foundation
 		bool LockBeforeDate (NSDate limit);

 		[Export ("name")]
-		string Name { get; [NullAllowed] set; }
+		[NullAllowed]
+		string Name { get; set; }
 	}

 	[BaseType (typeof(NSObject))]
@ -13258,7 +13259,8 @@ namespace Foundation
 		bool LockWhenCondition (nint condition, NSDate limit);

 		[Export ("name")]
-		string Name { get; [NullAllowed] set; }
+		[NullAllowed]
+		string Name { get; set; }
 	}

 	[BaseType (typeof(NSObject))]
@ -13271,7 +13273,8 @@ namespace Foundation
 		bool LockBeforeDate (NSDate limit);

 		[Export ("name")]
-		string Name { get; [NullAllowed] set; }
+		[NullAllowed]
+		string Name { get; set; }
 	}

 	[BaseType (typeof(NSObject))]
@ -13290,7 +13293,8 @@ namespace Foundation
 		void Broadcast ();

 		[Export ("name")]
-		string Name { get; [NullAllowed] set; }
+		[NullAllowed]
+		string Name { get; set; }
 	}

 // Not yet, the IntPtr[] argument isn't handled correctly by the generator (it tries to convert to NSArray, while the native method expects a C array).
--- a/src/gamekit.cs
+++ b/src/gamekit.cs
@ -500,7 +500,7 @@ namespace GameKit {
 		[NoWatch]
 		[Deprecated (PlatformName.iOS, 7, 0, message : "Use 'InitWithLeaderboardIdentifier' instead.")]
 		[Deprecated (PlatformName.MacOSX, 10, 10, message : "Use 'InitWithLeaderboardIdentifier' instead.")]
-		[Internal][NullAllowed]
+		[Internal]
 		[Export ("initWithCategory:")]
 		IntPtr InitWithCategory ([NullAllowed] string category);

@ -515,7 +515,7 @@ namespace GameKit {
 		IntPtr Constructor (string identifier, string playerID);

 		[iOS (7,0)][Mac (10,10)]
-		[Internal][NullAllowed]
+		[Internal]
 		[Export ("initWithLeaderboardIdentifier:")]
 		IntPtr InitWithLeaderboardIdentifier (string identifier);

--- a/src/gameplaykit.cs
+++ b/src/gameplaykit.cs
@ -1385,7 +1385,7 @@ namespace GameplayKit {
 		IGKRandom RandomSource { get; set; }

 		[Abstract]
-		[NullAllowed, Export ("bestMoveForActivePlayer")]
+		[Export ("bestMoveForActivePlayer")]
 		IGKGameModelUpdate GetBestMoveForActivePlayer ();
 	}

--- a/src/iad.cs
+++ b/src/iad.cs
@ -223,7 +223,6 @@ namespace iAd {
 		void SetCanDisplayBannerAds (bool value);

 		[iOS (7,0), Export ("originalContentView")]
-		[NullAllowed]
 		UIView GetOriginalContentView ();

 		[iOS (7,0), Export ("isPresentingFullScreenAd")]
--- a/src/intents.cs
+++ b/src/intents.cs
@ -2980,7 +2980,7 @@ namespace Intents {
 		INImage GetImage (string parameterName);

 		[Watch (5,0), Mac (10,14, onlyOn64: true), iOS (12,0)]
-		[NullAllowed, Export ("keyImage")]
+		[Export ("keyImage")]
 		INImage GetKeyImage ();
 	}

@ -6340,7 +6340,7 @@ namespace Intents {
 	[BaseType (typeof (NSUserActivity))]
 	interface NSUserActivity_IntentsAdditions {

-		[NullAllowed, Export ("interaction")]
+		[Export ("interaction")]
 		INInteraction GetInteraction ();
 	}

--- a/src/mapkit.cs
+++ b/src/mapkit.cs
@ -116,10 +116,11 @@ namespace MapKit {
 	
 		[Export ("annotation", ArgumentSemantic.Retain)]
 		[ThreadSafe] // Sometimes iOS will request the annotation from a non-UI thread (see https://bugzilla.xamarin.com/show_bug.cgi?27609)
+		[NullAllowed]
 #if XAMCORE_2_0
-		IMKAnnotation Annotation { get; [NullAllowed] set; }
+		IMKAnnotation Annotation { get; set; }
 #else
-		NSObject Annotation { get; [NullAllowed] set; }
+		NSObject Annotation { get; set; }
 #endif
 	
 		[Export ("image", ArgumentSemantic.Retain)]
--- a/src/mediaplayer.cs
+++ b/src/mediaplayer.cs
@ -2214,11 +2214,11 @@ namespace MediaPlayer {
 	[TV (10,0,1)][iOS (10,1)]
 	[NoWatch][NoMac]
 	interface NSUserActivity_MediaPlayerAdditions {
-		[NullAllowed, Export ("externalMediaContentIdentifier")]
+		[Export ("externalMediaContentIdentifier")]
 		NSString GetExternalMediaContentIdentifier ();

-		[NullAllowed, Export ("setExternalMediaContentIdentifier:")]
-		void SetExternalMediaContentIdentifier (NSString identifier);
+		[Export ("setExternalMediaContentIdentifier:")]
+		void SetExternalMediaContentIdentifier ([NullAllowed] NSString identifier);
 	}
 #endif
 	[iOS (9,0)][TV (9,0)]
@ -2227,7 +2227,7 @@ namespace MediaPlayer {
 	[Category]
 	[BaseType (typeof (AVMediaSelectionOption))]
 	interface AVMediaSelectionOption_MPNowPlayingInfoLanguageOptionAdditions {
-		[NullAllowed, Export ("makeNowPlayingInfoLanguageOption")]
+		[Export ("makeNowPlayingInfoLanguageOption")]
 		MPNowPlayingInfoLanguageOption CreateNowPlayingInfoLanguageOption ();
 	}

--- a/src/metal.cs
+++ b/src/metal.cs
@ -1040,14 +1040,16 @@ namespace Metal {
 #if XAMCORE_4_0
 		[Abstract]
 #endif
-		[NullAllowed, Export ("newEvent")]
+		[return: NullAllowed]
+		[Export ("newEvent")]
 		IMTLEvent CreateEvent ();

 		[Mac (10, 14, onlyOn64: true), iOS (12, 0), TV (12,0)]
 #if XAMCORE_4_0
 		[Abstract]
 #endif
-		[NullAllowed, Export ("newSharedEvent")]
+		[return: NullAllowed]
+		[Export ("newSharedEvent")]
 		IMTLSharedEvent CreateSharedEvent ();

 		[Mac (10,14, onlyOn64: true), iOS (12,0), TV (12,0)]
@ -1307,7 +1309,8 @@ namespace Metal {
 #if XAMCORE_4_0
 		[Abstract]
 #endif
-		[NullAllowed, Export ("newSharedTextureHandle")]
+		[return: NullAllowed]
+		[Export ("newSharedTextureHandle")]
 		MTLSharedTextureHandle CreateSharedTextureHandle ();
 	}
 	
--- a/src/modelio.cs
+++ b/src/modelio.cs
@ -124,7 +124,7 @@ namespace ModelIO {
 		bool ExportAssetToUrl (NSUrl url, out NSError error);

 		[TV (11,0), Mac (10,13, onlyOn64: true), iOS (11,0)]
-		[Export ("objectAtPath:"), NullAllowed]
+		[Export ("objectAtPath:")]
 		MDLObject GetObject (string atPath);

 		[Static]
@ -1715,10 +1715,12 @@ namespace ModelIO {
 		[return: NullAllowed]
 		CGImage GetImageFromTexture (nuint level);

-		[NullAllowed, Export ("texelDataWithTopLeftOrigin")]
+		[Export ("texelDataWithTopLeftOrigin")]
+		[return: NullAllowed]
 		NSData GetTexelDataWithTopLeftOrigin ();

-		[NullAllowed, Export ("texelDataWithBottomLeftOrigin")]
+		[Export ("texelDataWithBottomLeftOrigin")]
+		[return: NullAllowed]
 		NSData GetTexelDataWithBottomLeftOrigin ();

 		[Export ("texelDataWithTopLeftOriginAtMipLevel:create:")]
--- a/src/scenekit.cs
+++ b/src/scenekit.cs
@ -1716,7 +1716,8 @@ namespace SceneKit {
 		SCNCamera Camera { get; set;  }

 		[Export ("geometry", ArgumentSemantic.Retain)]
-		SCNGeometry Geometry { get; [NullAllowed] set;  }
+		[NullAllowed]
+		SCNGeometry Geometry { get; set; }

 		[NullAllowed] // by default this property is null
 		[Export ("name", ArgumentSemantic.Copy)]
@ -1782,7 +1783,8 @@ namespace SceneKit {

 		[Mac (10,9)]
 		[Export ("constraints", ArgumentSemantic.Copy)]
-		SCNConstraint [] Constraints { get; [NullAllowed] set; }
+		[NullAllowed]
+		SCNConstraint [] Constraints { get; set; }

 		[NoWatch, Mac (10, 9)]
 		[NullAllowed] // by default this property is null
@ -3897,7 +3899,8 @@ namespace SceneKit {
 		[Abstract]
 		[Mac (10,10), iOS (8,0)]
 		[Export ("technique", ArgumentSemantic.Copy)]
-		SCNTechnique Technique { get; [NullAllowed] set; }
+		[NullAllowed]
+		SCNTechnique Technique { get; set; }
 	}

 	[Watch (3,0)]
--- a/src/storekit.cs
+++ b/src/storekit.cs
@ -311,11 +311,11 @@ namespace StoreKit {
 	[BaseType (typeof (NSObject), Delegates=new string [] {"WeakDelegate"}, Events=new Type [] {typeof (SKRequestDelegate)})]
 	interface SKRequest {
 		[Export ("delegate", ArgumentSemantic.Weak)][NullAllowed]
-		NSObject WeakDelegate { get; [NullAllowed] set; }
+		NSObject WeakDelegate { get; set; }

 		[Wrap ("WeakDelegate")]
 		[Protocolize]
-		SKRequestDelegate Delegate { get; [NullAllowed] set; }
+		SKRequestDelegate Delegate { get; set; }

 		[Export ("cancel")]
 		void Cancel ();
@ -372,11 +372,11 @@ namespace StoreKit {
 		IntPtr Constructor (NSSet productIdentifiersStringSet);
 		
 		[Export ("delegate", ArgumentSemantic.Weak)][NullAllowed][New]
-		NSObject WeakDelegate { get; [NullAllowed] set; }
+		NSObject WeakDelegate { get; set; }

 		[Wrap ("WeakDelegate")][New]
 		[Protocolize]
-		SKProductsRequestDelegate Delegate { get; [NullAllowed] set; }
+		SKProductsRequestDelegate Delegate { get; set; }
 	}
 	
 	[BaseType (typeof (NSObject))]
--- a/src/uikit.cs
+++ b/src/uikit.cs
@ -591,7 +591,7 @@ namespace UIKit {
 		IntPtr _FirstAnchor<AnchorType> ();
 	
 		[iOS (10,0), TV (10,0)]
-		[NullAllowed, Export ("secondAnchor", ArgumentSemantic.Copy)]
+		[Export ("secondAnchor", ArgumentSemantic.Copy)]
 		[Internal]
 		IntPtr _SecondAnchor<AnchorType> ();
 #endif
@ -3690,7 +3690,8 @@ namespace UIKit {
 		UICollectionViewDataSource DataSource { get; set; }

 		[Export ("backgroundView", ArgumentSemantic.Retain)]
-		UIView BackgroundView { get; [NullAllowed] set; }
+		[NullAllowed]
+		UIView BackgroundView { get; set; }

 		[Export ("allowsSelection")]
 		bool AllowsSelection { get; set;  }
@ -7359,7 +7360,8 @@ namespace UIKit {
 		UIBezierPath FromRoundedRect (CGRect rect, nfloat cornerRadius);

 		[Export ("CGPath")]
-		CGPath CGPath { get; [NullAllowed] set; }
+		[NullAllowed]
+		CGPath CGPath { get; set; }

 		[Export ("moveToPoint:")]
 		void MoveTo (CGPoint point);
@ -7760,13 +7762,16 @@ namespace UIKit {
 		UIDatePickerMode Mode { get; set; }

 		[Export ("locale", ArgumentSemantic.Retain)]
-		NSLocale Locale { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSLocale Locale { get; set; }

 		[Export ("timeZone", ArgumentSemantic.Retain)]
-		NSTimeZone TimeZone { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSTimeZone TimeZone { get; set; }

 		[Export ("calendar", ArgumentSemantic.Copy)]
-		NSCalendar Calendar { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSCalendar Calendar { get; set; }

 		// not fully clear from docs but null is not allowed:
 		// Objective-C exception thrown.  Name: NSInternalInconsistencyException Reason: Invalid parameter not satisfying: date
@ -7774,10 +7779,12 @@ namespace UIKit {
 		NSDate Date { get; set; }
 		
 		[Export ("minimumDate", ArgumentSemantic.Retain)]
-		NSDate MinimumDate { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSDate MinimumDate { get; set; }
 		
 		[Export ("maximumDate", ArgumentSemantic.Retain)]
-		NSDate MaximumDate { get; [NullAllowed] set; }
+		[NullAllowed]
+		NSDate MaximumDate { get; set; }

 		[Export ("countDownDuration")]
 		double CountDownDuration { get; set; }
@ -8414,7 +8421,7 @@ namespace UIKit {
 		UIBarButtonItem BackBarButtonItem { get; set; }

 		[Export ("titleView", ArgumentSemantic.Retain), NullAllowed]
-		UIView TitleView { get; [NullAllowed] set; }
+		UIView TitleView { get; set; }

 		[NoTV]
 		[Export ("prompt", ArgumentSemantic.Copy), NullAllowed]
@ -10890,7 +10897,8 @@ namespace UIKit {

 		[NoTV]
 		[Export ("customizableViewControllers", ArgumentSemantic.Copy)]
-		UIViewController [] CustomizableViewControllers { get; [NullAllowed]  set; }
+		[NullAllowed]
+		UIViewController [] CustomizableViewControllers { get; set; }

 		[Export ("tabBar")]
 		UITabBar TabBar { get; }
@ -11685,7 +11693,7 @@ namespace UIKit {
 		UITableViewCellAccessory Accessory { get; set; }

 		[Export ("accessoryView", ArgumentSemantic.Retain)][NullAllowed]
-		UIView AccessoryView { get; [NullAllowed] set; }
+		UIView AccessoryView { get; set; }
 		
 		[Export ("editingAccessoryType")]
 		UITableViewCellAccessory EditingAccessory { get; set; }
@ -12030,13 +12038,16 @@ namespace UIKit {
 		IntPtr Constructor (CGRect frame);

 		[Export ("text", ArgumentSemantic.Copy)]
-		string Text { get; [NullAllowed] set; }
+		[NullAllowed]
+		string Text { get; set; }

 		[Export ("textColor", ArgumentSemantic.Retain)]
-		UIColor TextColor { get; [NullAllowed] set; }
+		[NullAllowed]
+		UIColor TextColor { get; set; }

 		[Export ("font", ArgumentSemantic.Retain)]
-		UIFont Font { get; [NullAllowed] set; }
+		[NullAllowed]
+		UIFont Font { get; set; }

 		[Export ("textAlignment")]
 		UITextAlignment TextAlignment { get; set; }
@ -12045,7 +12056,8 @@ namespace UIKit {
 		UITextBorderStyle BorderStyle { get; set; }

 		[Export ("placeholder", ArgumentSemantic.Copy)]
-		string Placeholder { get; [NullAllowed] set; }
+		[NullAllowed]
+		string Placeholder { get; set; }

 		[Export ("clearsOnBeginEditing")]
 		bool ClearsOnBeginEditing { get; set; }
@ -12057,17 +12069,19 @@ namespace UIKit {
 		nfloat MinimumFontSize { get; set; }

 		[Export ("delegate", ArgumentSemantic.Assign)][NullAllowed]
-		NSObject WeakDelegate { get; [NullAllowed] set; }
+		NSObject WeakDelegate { get; set; }

 		[Wrap ("WeakDelegate")]
 		[Protocolize]
-		UITextFieldDelegate Delegate { get; [NullAllowed] set; }
+		UITextFieldDelegate Delegate { get; set; }

 		[Export ("background", ArgumentSemantic.Retain)]
-		UIImage Background { get; [NullAllowed] set; }
+		[NullAllowed]
+		UIImage Background { get; set; }

 		[Export ("disabledBackground", ArgumentSemantic.Retain)]
-		UIImage DisabledBackground { get; [NullAllowed] set; }
+		[NullAllowed]
+		UIImage DisabledBackground { get; set; }

 		[Export ("isEditing")]
 		bool IsEditing { get; }
@ -13473,7 +13487,8 @@ namespace UIKit {

 		// These come from @interface UIViewController (UINavigationControllerContextualToolbarItems)
 		[Export ("toolbarItems", ArgumentSemantic.Retain)]
-		UIBarButtonItem [] ToolbarItems { get; [NullAllowed] set; }
+		[NullAllowed]
+		UIBarButtonItem [] ToolbarItems { get; set; }

 		[NoTV]
 		[Export ("setToolbarItems:animated:")][PostGet ("ToolbarItems")]
@ -16278,7 +16293,8 @@ namespace UIKit {
 		NSAttributedString GetAccessibilityAttributedContent (nint lineNumber);

 		[TV (11,0), iOS (11,0)]
-		[NullAllowed, Export ("accessibilityAttributedPageContent")]
+		[Export ("accessibilityAttributedPageContent")]
+		[return: NullAllowed]
 		NSAttributedString GetAccessibilityAttributedPageContent ();
 	}