Best practices: MUST NOT use "return"

The return statement from Java signals a side-effect - unwind the stack and give this value to the caller. In a language in which the emphasis is on side-effect-full programming, this makes sense. However Scala is an expression-oriented language in which the emphasis is on controlling/limiting side-effects and return is not idiomatic.
To make matters worse, return probably doesn't behave as you think it does.
A return statement inside a nested anonymous function is implemented by throwing and catching a NonLocalReturnException.
Besides, return is anti-structural programming, as functions can be described with multiple exit points and if you need return, like in those gigantic methods with lots of if/else branches, the presence of a return is a clear signal that the code stinks, a magnet for future bugs and is thus in urgent need of refactoring.
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