Covariant arrays. Blurgh.

covariant.ts

// Compiles fine even though the code is broken.
// This is because arrays are covariant and mutable.
//
// TypeScript team: Please fix either of those things. Preferably mutability :)

class Animal {}

class Snake extends Animal {
    slither() {
        alert("Slithering!")
    }
}

class Horse extends Animal {}

var a: Snake[] = [new Snake()]
var b: Animal[] = a
b[0] = new Horse()

var notASnake: Snake = a[0]
notASnake.slither()