> Strongly typed and weakly typed do not seem to have good definitions.
Is strongly typed not “I compiler/runtime guarantee the bytes I read adhere to type T”?
Is strongly typed not “I compiler/runtime guarantee the bytes I read adhere to type T”?
In Typescript this is by design. The most obvious is array variance. Typescript makes them covariant because that's what a lot of sane TS and JS code uses them as, but they should be invariant because you can write to them.
Example:
const dogs: Dog[] = []
// A sound type system would error here,
// but there's too many useful cases where you want to do this
const animals: Animal[] = dogs
animals.push(new Cat())
animals[0].bark() // runtime TypeError here class Animal { }
class Dog extends Animal{
bark(){return 1}
}
class Cat extends Animal{
bark(){return 1}
}
const dogs: Dog[] = []
const animals: Animal[] = dogs
animals.push(new Cat())
animals[0].bark() <<<<< "Property 'bark' does not exist on type 'Animal'."I didn't go to college for software engineering or anything so when I ran into that for the first time I assumed there must have been some good academic reason that was simply beyond me as to why it was done that way.
It turns out that no, it's just as weird to those that do have the formal background, boy am I feeling vindicated ;)