class RuboCop::Cop::Layout::SpaceAroundBlockParameters

def check_arg(arg)
  arg.children.each { |a| check_arg(a) } if arg.mlhs_type?
  expr = arg.source_range
  check_no_space(
    range_with_surrounding_space(expr, side: :left).begin_pos,
    expr.begin_pos - 1,
    'Extra space before'
  )
end