class RuboCop::Cop::Style::NonNilCheck

end
!current_user.nil?
def signed_in?
# good
Non-nil checks are allowed if they are the final nodes of predicate.
if x
# good (when allowing semantic changes)
if !x.nil?
# bad (when allowing semantic changes)
# good (when not allowing semantic changes)
if x != nil
# bad
@example
This cop checks for non-nil checks, which are usually redundant.

def autocorrect(node) 

def autocorrect(node)
  receiver, method, _args = *node
  if method == :!=
    autocorrect_comparison(node)
  elsif method == :!
    autocorrect_non_nil(node, receiver)
  end
end

def autocorrect_comparison(node) 

def autocorrect_comparison(node)
  @corrections << lambda do |corrector|
    expr = node.loc.expression
    new_code =
      if include_semantic_changes?
        expr.source.sub(/\s*!=\s*nil/, '')
      else
        expr.source.sub(/^(\S*)\s*!=\s*nil/, '!\1.nil?')
      end
    corrector.replace(expr, new_code)
  end
end

def autocorrect_non_nil(node, inner_node) 

def autocorrect_non_nil(node, inner_node)
  @corrections << lambda do |corrector|
    receiver, _method, _args = *inner_node
    if receiver
      corrector.replace(node.loc.expression,
                        receiver.loc.expression.source)
    else
      corrector.replace(node.loc.expression, 'self')
    end
  end
end

def include_semantic_changes? 

def include_semantic_changes?
  cop_config['IncludeSemanticChanges']
end

def message(node) 

def message(node)
  _receiver, method, _args = *node
  if method == :!=
    'Prefer `!expression.nil?` over `expression != nil`.'
  else
    'Explicit non-nil checks are usually redundant.'
  end
end

def nil_check?(node) 

def nil_check?(node)
  return false unless node && node.type == :send
  _receiver, method, *_args = *node
  method == :nil?
end

def on_method_def(_node, name, _args, body) 

def on_method_def(_node, name, _args, body)
  # only predicate methods are handled differently
  return unless name.to_s.end_with?('?')
  return unless body
  if body.type != :begin
    ignore_node(body)
  elsif body.type == :begin
    ignore_node(body.children.last)
  end
end

def on_send(node) 

def on_send(node)
  return if ignored_node?(node)
  receiver, method, args = *node
  if method == :!=
    add_offense(node, :selector) if args == NIL_NODE
  elsif method == :! && include_semantic_changes?
    add_offense(node, :expression) if nil_check?(receiver)
  end
end