Thanks for "When Polymorphism Fails" link, it was a wonderful read. I've actually run into such situations a couple of times - but in my experience, you want most of your methods to be statically checked, and only a minority of them to be added and checked dynamically in runtime. May be the solution is to have two different method tables, that look and behave in a different way?
However I will point out that probably 80% of the world's top websites are written in dynamic languages -- Wikipedia, Facebook, Yahoo, YouTube, Reddit, etc. (that's not even counting the JavaScript.)
So there is something about that use case and dynamic languages... That's not to say a language is great because it's used widely. But it means that it must be getting something right, and not doing other things too badly.
So yeah all I'm saying is that there's a tradeoff. If there's was no tradeoff, then it would have never have swung toward dynamic languages in the 90's/2000's. It's not like we didn't have statically typed languages before the web. But things swung that way, and it sounds like they're swinging back, with PHP, Python, and JavaScript all getting optional types in one way or another.
Type Checking vs. Metaprogramming: http://www.oilshell.org/blog/2016/12/05.html
http://www.oilshell.org/blog/2017/01/21.html (at the end, pretty printing requires metaprogramming, or escaping into another language)
Whenever you have a code generator like an ORM, or protobuf-like schema languages, you can use metaprogramming instead. Generally I think this helps the program so you don't have these impenetrable walls between layers, where one person understands one side and the other person understands the other.
I find that a lot of programmers coming from statically typed languages are writing Java in Python, or Java in JavaScript. In Java you don't really think in terms of metaprogramming.
If that's the case, then it is going to feel annoying. You're getting all the downsides without any of the upsides.
I would look at Go for other examples of the downsides -- namely the lack of generics. Go is attracting a lot of Python and Ruby programmers.
In Go, you can't write basic generic functions like max(), map(), filter(), and sort() -- in JavaScript and other dynamic languages this is not something you would think twice about.
I guess between metaprogramming and generics, dynamic languages let you write more abstract and concise programs. Programming in statically typed languages feels repetitive to me, and the architecture is quite clunky unless you are doing textual code generation.
Steve Yegge also has a bunch of good posts about dynamic languages.
Thanks for the honest question. I think it's important to remember that there are tradeoffs. I fully admit that type checking is useful in many circumstances. I would like the best of both worlds. I'm a little disappointed that recent hybrid languages like Dart and to some extent Racket have had problems with optional typing and gradual typing. It is something I'm interested in but it seems like an unsolved problem.