Nested Blocks

Curly Braces

Opening curly braces ({) must be on the same line as the declaration they represent:

def foo = {
  ...
}

Technically, Scala’s parser does support GNU-style notation with opening braces on the line following the declaration. However, the parser is not terribly predictable when dealing with this style due to the way in which semi-colon inference is implemented. Many headaches will be saved by simply following the curly brace convention demonstrated above.

Parentheses

In the rare cases when parenthetical blocks wrap across lines, the opening and closing parentheses should be unspaced and generally kept on the same lines as their content (Lisp-style):

(this + is a very ++ long *
  expression)

Parentheses also serve to disable semicolon inference, and so allow the developer to start lines with operators, which some prefer:

(  someCondition
|| someOtherCondition
|| thirdCondition
)

A trailing parenthesis on the following line is acceptable in this case, for aesthetic reasons.