Some automatic conversion is fine.

a=3+0.2

print("Hello {name}. You are {age} years old")

That kind of thing. But the principle of least surprise definitely applies. If you get to the point where you're adding two booleans and a string, I feel like the language should at least say something. At least until the technology exists for it to physically reach out of your screen and slap you.

You don't necessarily need types for that kind of thing though, a strict linter that flags that code works just as well