1.1.4.1. nullability.NullPassedToNonnull (ObjC)
Warns when a null pointer is passed to a pointer which has a _Nonnull type.

Examples:

if (name != nil)
  return;
// Warning: nil passed to a callee that requires a non-null 1st parameter
NSString *greeting = [@"Hello " stringByAppendingString:name];