Fix some static analyzer warnings (facebookarchive#2999)

Author: maicki

AsyncDisplayKit/ASDisplayNode.mm

@@ -3826,7 +3826,7 @@ - (CGRect)_frameInWindow
 
   if (self.layerBacked) {
     CALayer *rootLayer = _layer;
-    CALayer *nextLayer = rootLayer;
+    CALayer *nextLayer = nil;
     while ((nextLayer = rootLayer.superlayer) != nil) {
       rootLayer = nextLayer;
     }

AsyncDisplayKit/ASNetworkImageNode.mm

@@ -414,17 +414,22 @@ - (void)_updateProgressImageBlockOnDownloaderIfNeeded
     } callbackQueue:dispatch_get_main_queue() withDownloadIdentifier:newDownloadIDForProgressBlock];
   }
 
-  // Update state.
+  // Update state local state with lock held.
   {
     ASDN::MutexLocker l(__instanceLock__);
+    // Check if the oldDownloadIDForProgressBlock still is the same as the _downloadIdentifierForProgressBlock
     if (_downloadIdentifierForProgressBlock == oldDownloadIDForProgressBlock) {
       _downloadIdentifierForProgressBlock = newDownloadIDForProgressBlock;
-    } else {
+    } else if (newDownloadIDForProgressBlock != nil) {
+      // If this is not the case another thread did change the _downloadIdentifierForProgressBlock already so
+      // we have to deregister the newDownloadIDForProgressBlock that we registered above
       clearAndReattempt = YES;
     }
   }
 
   if (clearAndReattempt) {
+    // In this case another thread changed the _downloadIdentifierForProgressBlock before we finished registering
+    // the new progress block for newDownloadIDForProgressBlock ID. Let's clear it now and reattempt to register
     [_downloader setProgressImageBlock:nil callbackQueue:dispatch_get_main_queue() withDownloadIdentifier:newDownloadIDForProgressBlock];
     [self _updateProgressImageBlockOnDownloaderIfNeeded];
   }

AsyncDisplayKit/Details/ASCollectionDataController.h

@@ -44,7 +44,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (instancetype)initWithDataSource:(id<ASCollectionDataControllerSource>)dataSource eventLog:(nullable ASEventLog *)eventLog NS_DESIGNATED_INITIALIZER;
 
-- (ASCellNode *)supplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
+- (nullable ASCellNode *)supplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
 
 - (nullable id<ASSectionContext>)contextForSection:(NSInteger)section;
 

AsyncDisplayKit/Details/ASCollectionInternal.h

@@ -39,7 +39,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @param indexPath The index path of the row.
  */
-- (NSIndexPath *)convertIndexPathToCollectionNode:(NSIndexPath *)indexPath;
+- (nullable NSIndexPath *)convertIndexPathToCollectionNode:(NSIndexPath *)indexPath;
 
 /**
  * Attempt to get the node index paths given the view-layer index paths.

AsyncDisplayKit/Details/ASObjectDescriptionHelpers.h

@@ -59,7 +59,7 @@ NSString *ASObjectDescriptionMake(__autoreleasing id object, NSArray<NSDictionar
  * Note: `object` param is autoreleasing so that this function is dealloc-safe.
  *   No, unsafe_unretained isn't acceptable here – the optimizer may deallocate object early.
  */
-NSString *ASObjectDescriptionMakeTiny(__autoreleasing id object);
+NSString *ASObjectDescriptionMakeTiny(__autoreleasing id _Nullable object);
 
 NSString * _Nullable ASStringWithQuotesIfMultiword(NSString * _Nullable string);
 

AsyncDisplayKit/Private/ASInternalHelpers.h

@@ -51,7 +51,7 @@ CGFloat ASRoundPixelValue(CGFloat f);
 
 BOOL ASClassRequiresMainThreadDeallocation(Class _Nullable c);
 
-Class _Nullable ASGetClassFromType(const char *type);
+Class _Nullable ASGetClassFromType(const char * _Nullable type);
 
 ASDISPLAYNODE_EXTERN_C_END
 

AsyncDisplayKit/Private/ASInternalHelpers.m

@@ -124,7 +124,7 @@ BOOL ASClassRequiresMainThreadDeallocation(Class c)
   return NO;
 }
 
-Class _Nullable ASGetClassFromType(const char *type)
+Class _Nullable ASGetClassFromType(const char  * _Nullable type)
 {
   // Class types all start with @"
   if (type == NULL || strncmp(type, "@\"", 2) != 0) {

AsyncDisplayKit/UIImage+ASConvenience.h

@@ -32,7 +32,7 @@ NS_ASSUME_NONNULL_BEGIN
  * @param fillColor    The fill color of the rounded-corner image
  */
 + (UIImage *)as_resizableRoundedImageWithCornerRadius:(CGFloat)cornerRadius
-                                          cornerColor:(UIColor *)cornerColor
+                                          cornerColor:(nullable UIColor *)cornerColor
                                             fillColor:(UIColor *)fillColor AS_WARN_UNUSED_RESULT;
 
 /**
@@ -62,7 +62,7 @@ NS_ASSUME_NONNULL_BEGIN
  * @param scale           The number of pixels per point. Provide 0.0 to use the screen scale.
  */
 + (UIImage *)as_resizableRoundedImageWithCornerRadius:(CGFloat)cornerRadius
-                                          cornerColor:(UIColor *)cornerColor
+                                          cornerColor:(nullable UIColor *)cornerColor
                                             fillColor:(UIColor *)fillColor
                                           borderColor:(nullable UIColor *)borderColor
                                           borderWidth:(CGFloat)borderWidth