class RuboCop::Cop::Style::VariableInterpolation

def autocorrect(node)
  @corrections << lambda do |corrector|
    expr = node.loc.expression
    corrector.replace(expr, "{#{expr.source}}")
  end
end

def check_for_interpolation(node)
  var_nodes(node.children).each do |v|
    var = v.loc.expression.source
    add_offense(v, :expression, format(MSG, var, var))
  end
end

def on_dstr(node)
  check_for_interpolation(node)
end

def on_regexp(node)
  check_for_interpolation(node)
end

def on_xstr(node)
  check_for_interpolation(node)
end

def var_nodes(nodes)
  nodes.select { |n| [:ivar, :cvar, :gvar, :nth_ref].include?(n.type) }
end