The argument seems to be that if the added type system is not perfect, then it will be useless. For a working counterexample, see the Closure Compiler (https://

The argument seems to be that if the added type system is not perfect, then it will be useless. For a working counterexample, see the Closure Compiler (https://github.com/google/closure-compiler https://github.com/google/closure-compiler), which adds a bolt-on, underspecified, occasionally-changing type system to Javascript. Similarly to GvR's proposal (https://mail.python.org/pipermail/python-ideas/2014-August/028618.html https://mail.python.org/pipermail/python-ideas/2014-August/0...), the types are only ever checked at compile time: there's no attempt to use them as runtime assertions and very limited attempts to use them for compile-time improvements. So, yes, because they are imperfect and optional, you don't catch every type error, and you need to add type hints / casts that in a perfect system wouldn't be necessary. Is this kind of flawed type system worth it? Hell yes. I've maintained large programs in both Python and (closure-compiled) Javascript, and with the former I've wished I had the help of the limited type checking available in the latter.