Parenthesis in trailing closure rule

[marcelofabri]

When using trailing closures, one can add () after the method call, but that should be discouraged.

let x = [1, 2]

// shouldn't trigger
_ = x.map { $0 + 1 }

// should trigger
_ = x.map() { $0 + 1 }

Note that there are cases when parenthesis are allowed (when there're more than 1 parameter):

// shouldn't trigger
_ = x.reduce(0) { $0 + $1 }

[jpsim]

EmptyParenthesesWithTrailingClosureRule. A bit verbose, but descriptive.