Fabric: Better error reporting in UIView+ComponentViewProtocol

Summary:
We need this to make crash logs more actionable. For now we know that those asserts fire so we should make them actionable.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: sammy-SC

Differential Revision: D23580103

fbshipit-source-id: 8532e33b016e738a4f128c9b547c33d204610bcc

React/Fabric/Mounting/UIView+ComponentViewProtocol.mm

@@ -30,16 +30,29 @@ + (ComponentDescriptorProvider)componentDescriptorProvider
 
 - (void)mountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index
 {
-  RCTAssert(childComponentView.superview == nil, @"Attempt to mount already mounted component view.");
+  RCTAssert(
+      childComponentView.superview == nil,
+      @"Attempt to mount already mounted component view. (parent: %@, child: %@, index: %@)",
+      self,
+      childComponentView,
+      @(index));
   [self insertSubview:childComponentView atIndex:index];
 }
 
 - (void)unmountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index
 {
-  RCTAssert(childComponentView.superview == self, @"Attempt to unmount improperly mounted component view.");
   RCTAssert(
-      [self.subviews objectAtIndex:index] == childComponentView,
-      @"Attempt to unmount improperly mounted component view.");
+      childComponentView.superview == self,
+      @"Attempt to unmount a view which is mounted inside different view. (parent: %@, child: %@, index: %@)",
+      self,
+      childComponentView,
+      @(index));
+  RCTAssert(
+      (self.subviews.count > index) && [self.subviews objectAtIndex:index] == childComponentView,
+      @"Attempt to unmount a view which has a different index. (parent: %@, child: %@, index: %@)",
+      self,
+      childComponentView,
+      @(index));
 
   [childComponentView removeFromSuperview];
 }