Improve nullable annotations for _ASDisplayLayer and _ASDisplayView #trivial

Source/Details/_ASDisplayLayer.h

@@ -19,6 +19,8 @@
 #import <AsyncDisplayKit/ASBaseDefines.h>
 #import <AsyncDisplayKit/ASBlockTypes.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
 @class ASDisplayNode;
 @protocol _ASDisplayLayerDelegate;
 
@@ -28,7 +30,7 @@
  @discussion This property overrides the CALayer category method which implements this via associated objects.
  This should result in much better performance for _ASDisplayLayers.
  */
-@property (nonatomic, weak) ASDisplayNode *asyncdisplaykit_node;
+@property (nullable, nonatomic, weak) ASDisplayNode *asyncdisplaykit_node;
 
 /**
  @summary Set to YES to enable asynchronous display for the receiver.
@@ -57,7 +59,7 @@
 
  @desc The asyncDelegate will have the opportunity to override the methods related to async display.
  */
-@property (atomic, weak) id<_ASDisplayLayerDelegate> asyncDelegate;
+@property (nullable, atomic, weak) id<_ASDisplayLayerDelegate> asyncDelegate;
 
 /**
  @summary Suspends both asynchronous and synchronous display of the receiver if YES.
@@ -109,15 +111,19 @@
  @param isCancelledBlock Execute this block to check whether the current drawing operation has been cancelled to avoid unnecessary work. A return value of YES means cancel drawing and return.
  @param isRasterizing YES if the layer is being rasterized into another layer, in which case drawRect: probably wants to avoid doing things like filling its bounds with a zero-alpha color to clear the backing store.
  */
-+ (void)drawRect:(CGRect)bounds withParameters:(id)parameters isCancelled:(AS_NOESCAPE asdisplaynode_iscancelled_block_t)isCancelledBlock isRasterizing:(BOOL)isRasterizing;
++ (void)drawRect:(CGRect)bounds
+  withParameters:(nullable id)parameters
+     isCancelled:(AS_NOESCAPE asdisplaynode_iscancelled_block_t)isCancelledBlock
+   isRasterizing:(BOOL)isRasterizing;
 
 /**
  @summary Delegate override to provide new layer contents as a UIImage.
  @param parameters An object describing all of the properties you need to draw. Return this from -drawParametersForAsyncLayer:
  @param isCancelledBlock Execute this block to check whether the current drawing operation has been cancelled to avoid unnecessary work. A return value of YES means cancel drawing and return.
  @return A UIImage with contents that are ready to display on the main thread. Make sure that the image is already decoded before returning it here.
  */
-+ (UIImage *)displayWithParameters:(id<NSObject>)parameters isCancelled:(AS_NOESCAPE asdisplaynode_iscancelled_block_t)isCancelledBlock;
++ (UIImage *)displayWithParameters:(nullable id<NSObject>)parameters
+                       isCancelled:(AS_NOESCAPE asdisplaynode_iscancelled_block_t)isCancelledBlock;
 
 // Called on the main thread only
 
@@ -147,3 +153,5 @@
 - (void)cancelDisplayAsyncLayer:(_ASDisplayLayer *)asyncLayer;
 
 @end
+
+NS_ASSUME_NONNULL_END

Source/Details/_ASDisplayView.h

@@ -17,6 +17,8 @@
 
 #import <UIKit/UIKit.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
 // This class is only for use by ASDisplayNode and should never be subclassed or used directly.
 // Note that the "node" property is added to UIView directly via a category in ASDisplayNode.
 
@@ -28,7 +30,7 @@
  @discussion This property overrides the UIView category method which implements this via associated objects.
  This should result in much better performance for _ASDisplayView.
  */
-@property (nonatomic, weak) ASDisplayNode *asyncdisplaykit_node;
+@property (nullable, nonatomic, weak) ASDisplayNode *asyncdisplaykit_node;
 
 // These methods expose a way for ASDisplayNode touch events to let the view call super touch events
 // Some UIKit mechanisms, like UITableView and UICollectionView selection handling, require this to work
@@ -38,3 +40,5 @@
 - (void)__forwardTouchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;
 
 @end
+
+NS_ASSUME_NONNULL_END