class RuboCop::Cop::Style::BracesAroundHashParameters

def autocorrect(send_node)

otherwise.
the AST has changed, a braceless hash would not be parsed as a hash
node, because that context is needed. When parsing the code to see if
We let AutocorrectUnlessChangingAST#autocorrect work with the send 
def autocorrect(send_node)
  hash_node = send_node.last_argument
  lambda do |corrector|
    if hash_node.braces?
      remove_braces_with_whitespace(corrector, hash_node)
    else
      add_braces(corrector, hash_node)
    end
  end
end