Test code to check whether compiler-synthesized property setters actually assign anything if the new object equals the current one

DGPropertyEqualTest.m

#import <Foundation/Foundation.h>

@interface DGVeryEqual : NSObject
	@property(copy) NSString *desc;
	
	-(instancetype)initWithDescription:(NSString *)description;
@end

@implementation DGVeryEqual : NSObject
	-(instancetype)initWithDescription:(NSString *)description {
		self = [self init];
		if (self) {
			self.desc = description;
		}
		return self;
	}
	
	-(BOOL)isEqual:(id)object {
		return TRUE;
	}
	
	-(NSString *)description {
		return self.desc;
	}
@end

@interface DGPropertyHolder : NSObject
	@property(retain) DGVeryEqual *thing;
@end

@implementation DGPropertyHolder : NSObject
@end

int main(int argc, char **argv) {
	@autoreleasepool {
		DGVeryEqual *thing1 = [[DGVeryEqual alloc] initWithDescription:@"thing1"];
		DGVeryEqual *thing2 = [[DGVeryEqual alloc] initWithDescription:@"thing2"];
		NSLog(@"%@ %@", thing1, thing2);
		
		DGPropertyHolder *holder = [[DGPropertyHolder alloc] init];
		holder.thing = thing1;
		NSLog(@"%@", holder.thing);
		holder.thing = thing2;
		NSLog(@"%@", holder.thing);
	}
	return 0;
}