Edit: All of these edits to your posts after I've already replied are very confusing.
I'm more concerned about the effects of the post's title on people's programming practices than the actual content of it. HN does tend to have this effect unfortunately.
I don't want to get into this argument now though because it could last forever but hopefully it highlights why it's important to keep arguments tightly bounded and not make blanket statements when the domain is so large and complex and we can go off on a tangent in an infinite number of directions.
Ultimately, I enjoy JavaScript and I don't want future employers to force me to use TypeScript because of articles like yours (with those kinds of titles)... I was already forced to use TypeScript at my last company, it went well but it would have been even better if founders had let me and my team use JavaScript... For one, I might not have quit the company. I was tired of debugging mangled JavaScript (compiled from TS) using vim over SSH whenever there was a problem (it was a large decentralized P2P project so often that was the only way to debug it). The drawbacks of TS were definitely not worth its benefits for that specific project.
If you want to play with a powerful type system check out Raku. It offers gradual types that are a hybrid of dynamic and statically checked.
Basically, you can define a `subset` of a type with a validation predicate. Subsets can be named or anonymous and inline in function signatures.
Another thing that made me think of Raku was your discussion of NULLs. Any type container can be defined or undefined, an undefined Array container `isa` Array. But you can specify whether your annotation means to be specifically only defined or undefined members of the type. So `Int:D` is a defined integer, whereas `Int:U` is undefined, and `Int` is either.
The type specifications combined with multiple dispatch cam make for pretty code.
It's a really interesting language and, in my opinion, worth checking out. It would be great to hear your thoughts on it.
Personally, when I write a function definition, I always try to visualize the set of possible values that the function will need to handle - So given that I already have that precise set of possible arguments already in my mind as I write the function, it doesn't add any value for me to then formally generalize my function parameters as being integers or strings or some other types which are too broad to effectively constrain my function input to the required level. With static typed languages, merely specifying that a variable is an integer doesn't save me from having to think about what specific subset of integers I mean. For example, if my function only works with odd numbers as input, using the integer type definition will not offer me any additional safety.
I would argue that most functions are like this. The type definitions are never granular enough to guarantee correctness. The type system only protects you from the most basic/obvious mistakes - So obvious that you don't even need the type checker to tell you.
Static types only cover one set of bugs, but it is an extremely rewarding set. The payoff of static typing, and what TypeScript focuses on, is early feedback (did I get the name right, did I forget to convert some arguments, what can this value do?). If you focus on the "it eliminates some tests" aspect, you are completely missing the point.
> Personally, when I write a function definition, I always try to visualize the range of possible values that the function will need to handle - So given that I already have that specific range already in my mind as I write the function, it doesn't add any value...
So what the function will handle remain in your head? Or you found a better way to document them than type annotations? Do you write code that anyone else has to read now, or even you have to read later?
> The type definitions are never granular enough to guarantee correctness.
They were never meant for that purpose.