Crash due to LSP violation

LSPViolation.m

@interface Shape : NSObject
@end

@interface Circle : Shape
@end

@interface Triangle : Shape
- (BOOL)isEquilateral;
@end

@protocol BagOfShapes <NSObject>
@property Shape *shape;
@end

@interface BagOfTriangles : NSObject <BagOfShapes>
@property Triangle *shape;
@end


// Now in some other part of your code you do:
	BagOfTriangles *bagOfTriangles = [[BagOfTriangles alloc] init];
	id<BagOfShapes> bagOfShapes = bagOfTriangles;
	
	// Legal, Circle "is a" Shape, but you just got a Circle in a bag of triangles, be ready for the disaster
	bagOfShapes.shape = [[Circle alloc] init];
	
	// Crash: Unrecognized selector sent to instance
	[bagOfTriangles.shape isEquilateral];