TLDR: for productivity, there's basically no measurable impact detected in studies, positive or negative. For security and bugs, the impact is as expected: dynamic languages are as safe as strictly typed languages if they are paired with exhaustive test suites which enforce type safety. You can either write the type information alongside the application code, or write the test suite to enforce it.
Folks who think Dynamic Typing frees them of having to consider types are just fooling themselves; in this thread, even, the argument is that because they know what the types are then stating them is just unnecessary "noise". Which is all well and good, in the here and now, but provides no value when the code is foreign or forgotten; and with just a little additional syntax both the information is available to the programmer and the compiler can perform performance and security analysis with greater ease.
> for productivity, there's basically no measurable impact detected in studies, positive or negative
As I said, controversial at best.
But you're not being completely honest here. Most research is either inconclusive, or says dynamic is more productive. It is nearly impossible to find research that says static typing is more productive.
Which is quite obvious today, Uncle Bob and Steve Yegge were talking about this since 2000s.
I didn't even get to the function body, and I already used multiple levels of my mental stack. Ugh.
And gradual typing is the worst. It is either a terrible idea, or at least a terrible implementation (looking TS/mypy). It combines the worst of two worlds.
The only viable benefit of gradual typing is making dependency hierarchy explicit.
Get off the high horse, static vs dynamic has been a never ending debate since the dawn of time.
Just because you side with one religion doesn't automatically make it "well known". Learn to recognize your own biases.