alt Hacker NewsThat’s barely scratching the surface.
In TypeScript the following is also valid:
class Something{
value: Number
class SomethingElse{
value: Number
foo: String
bar: SomeOtherThing[]
function AddSomething(v: Something)
{
v.value += 1;
var ex = new SomethingElse{
value: 3,
foo: “TypeScript is fake types”,
bar: []
AddSomething(ex);
Why does it work? Because in TypeScript as long as you have a “shape” that fits, it’s the “same type.”
Complete and utter insanity to me, to pretend there’s any real type checking, when types are entirely fake and made up.
That's because it's structurally typed (as opposed to nominally typed). I don't happen to prefer it, but I don't think it's fair to conflate that with unsoundness like the example given above; it's totally possible to have a sound structural type system. TypeScript doesn't happen to be sound, but it's not because of that.