Wow, I have never heard of this in any language, and I think it would benefit every language.

I have been writing Python for almost twenty years, and while my rate of discovering things in the standard library has slowed down considerably, I still learn new subtleties all the time.

If I started on a new language, I'd have none of that, I'd make all the mistakes and without someone to correct me I'd never know better (reading code is how I discover a lot of it, but it takes a long time to read a lot of code).

More, I do an awful lot of code reviews and I'm constantly pointing out the same things: in Python it's use a comprehension here, this built-in function does what you want, use items(), use zip() - this would help.

A tool would get rid of the boring part of the job, allow faster progress.