[valcron1000]

> being flexible in what you accept when possible

I disagree with this. When working with rxjs I wanted to emit a single string in an error handler. Since strings are iterable I ended up with the characters being emitted.

The library authors added this "flexibility" (implicit conversion from values to observables) which caused a subtle bug that took me a while to figure out. A type error (expected observable, got string) would have prevented this.