class RuboCop::Cop::Lint::NumberedParameterAssignment

Checks for uses of numbered parameter assignment. It emulates the following warning in Ruby 2.7:

% ruby -ve '_1 = :value'
ruby 2.7.2p137 (2020-10-01 revision 5445e04352) [x86_64-darwin19]
-e:1: warning: `_1' is reserved for numbered parameter; consider another name

Assigning to a numbered parameter (from ‘_1` to `_9`) causes an error in Ruby 3.0.

% ruby -ve '_1 = :value'
ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin19]
-e:1: _1 is reserved for numbered parameter

NOTE: The parametered parameters are from ‘_1` to `_9`. This cop checks `_0`, and over `_10` as well to prevent confusion.

@example

# bad
_1 = :value

# good
non_numbered_parameter_name = :value

Constants

LVAR_MSG
NUMBERED_PARAMETER_RANGE
NUM_PARAM_MSG

Public Instance Methods

on_lvasgn(node) click to toggle source
# File lib/rubocop/cop/lint/numbered_parameter_assignment.rb, line 35
def on_lvasgn(node)
  lhs, _rhs = *node
  return unless /\A_(\d+)\z/ =~ lhs

  number = Regexp.last_match(1).to_i
  template = NUMBERED_PARAMETER_RANGE.include?(number) ? NUM_PARAM_MSG : LVAR_MSG

  add_offense(node, message: format(template, number: number))
end