Automatic argument checking about runtypes

[pelotom]

This sounds like the purpose of contracts, although I haven’t tried using them as a decorator. If there’s something that we could do to make them more idiomatic for that purpose I’d be open to it.

[yuhr]

Yes of course, so contracts look like:

method = Contract(Runtype1, Runtype2, Runtype3)
  .enforce((param1: Static1, param2: Static2, param3: Static3) => {
    ...
  })

However, my understanding is if one wants to write a single function then a contract should fit (and calling an external function may also fits), but for implementing class methods, usually there's no need to type-check the returning value as it is already in the internal type-safe world, that is, returning a member, a return value from another method, or something else which is try-caught or guarded within their mechanism.

And another advantage is that we can skip trailing params:

@checked(Runtype1, Runtype2)
method(param1: Static1, param2: Static2, param3: any) {
  ...
}

Also we can utilise parameter decorators for marking which params shall be type-checked:

@checked(Runtype1, Runtype3)
method(@check param1: Static1, param2: any, @check param3: Static3) {
  ...
}

or kind of

@checked
method(@check(Runtype1) param1: Static1, param2: any, @check(Runtype3) param3: Static3) {
  ...
}

We use Always in the case of contracts, but it's somewhat verbose I think.