alt Hacker News> You may notice no language on the planet does this. That is because it is bad.
Perhaps I've explained this poorly, but C#, Java, Perl, & Haskell (and I'm sure others as well) do versions of this already...
You even seem to imply that Swift does, though I have almost no experience directly with Swift.
The vast majority of times it is NOT ambiguous. The compiler can flag it, IFF you want it to.
If you're coming from Python and you want to ease your learning experience, you probably don't want to hit several brick walls before you can do anything...
If you have an enterprise codebase, you probably don't want to allow anything to be compiled that could be ambiguous, so you can force that mode of compilation (and likely should)...
I don't know of any major language which have progressive modes of compilation like this. I think people will find it useful.
Maybe it'll be a disaster. Time will tell. The whole point is to intelligent design the modes such that you can't ever get a MASSIVE surprise "upgrading" from one mode to the next, any error that is too hard to resolve basically automatically / through selecting options needs to be dealt with at the easiest mode.
In none of the languages you mentioned do stdlib functions either return an iterator or a list depending on whether you feed it into an iterator operation; in none of the languages you mentioned can a fully-generic return as a method receiver be inferred by the name of the method. It has nothing to do with how well you explained it; it just doesn't exist. Every single thing you are complaining about exists in all of the languages you brought up, although Perl does a small portion of that in some cases depending on the variable sigil (ie still not guessed).
Your post is a restricted special case of "it would be great if any old sequence of characters compiled correctly and the compiler just read my mind". Wouldn't it just, but the rules of programming languages exist for more purposes than just annoying the user.