Class: RuboCop::Cop::Lint::AmbiguousRange

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::RuboCop::Cop::AutoCorrector, ::RuboCop::Cop::Base, ::RuboCop::ExcludeLimit, NodePattern::Macros, RuboCop::AST::Sexp
Instance Chain:
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/lint/ambiguous_range.rb


Checks for ambiguous ranges.

Ranges have quite low precedence, which leads to unexpected behavior when using a range with other operators. This cop avoids that by making ranges explicit by requiring parenthesis around complex range boundaries (anything that is not a literal: numerics, strings, symbols, etc.).

This cop can be configured with RequireParenthesesForMethodChains in order to specify whether method chains (including self.foo) should be wrapped in parens by this cop.

Regardless of this configuration, if a method receiver is a basic literal value, it will be wrapped in order to prevent the ambiguity of 1..2.to_a.


# bad
x || 1..2
(x || 1..2)

# good, unambiguous

# good, ambiguity removed
x || (1..2)
(x || 1)..2
(x || 1)..(y || 2)

RequireParenthesesForMethodChains: false (default)

# good

RequireParenthesesForMethodChains: true

# bad

# good

Cop Safety Information:

  • The cop autocorrects by wrapping the entire boundary in parentheses, which makes the outcome more explicit but is possible to not be the intention of the programmer. For this reason, this cop’s autocorrect is unsafe (it will not change the behavior of the code, but will not necessarily match the intent of the program).

Constant Summary

::RuboCop::Cop::Base - Inherited


Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

::RuboCop::Cop::Base - Inherited

.gem_requirements, .lint?,

Returns if class supports autocorrect.


Override if your cop should be called repeatedly for multiple investigations Between calls to on_new_investigation and on_investigation_end, the result of processed_source will remain constant.

Class Method Summary

::RuboCop::Cop::Base - Inherited


List of cops that should not try to autocorrect at the same time as this cop.



.callbacks_needed, .cop_name, .department,

Returns an url to view this cops documentation online.


Call for abstract Cop classes.


Override and return the Force class(es) you need to join.


Returns true if the cop name or the cop namespace matches any of the given names.


Register a version requirement for the given gem name.


::RuboCop::ExcludeLimit - Extended


Sets up a configuration option to have an exclude limit tracked.


Instance Attribute Summary

Instance Method Summary

::RuboCop::Cop::Base - Inherited


Adds an offense that has no particular location.


Adds an offense on the specified range (or node with an expression) Unless that offense is disabled for this range, a corrector will be yielded to provide the cop the opportunity to autocorrect the offense.


Called before any investigation.


Configuration Helpers.

#cop_name, #excluded_file?,

This method should be overridden when a cop’s behavior depends on state that lives outside of these locations:


Gets called if no message is specified when calling add_offense or add_global_offense Cops are discouraged to override this; instead pass your message directly.


Alias for Base#cop_name.


Called after all on_…​


Called before all on_…​


Called instead of all on_…​


There should be very limited reasons for a Cop to do it’s own parsing.


Called between investigations.

#relevant_file?, #target_rails_version, #target_ruby_version, #annotate, #apply_correction, #attempt_correction,

Reserved for Cop::Cop.


Called to complete an investigation.

#correct, #current_corrector,

Reserved for Commissioner:

#current_offenses, #currently_disabled_lines, #custom_severity, #default_severity, #disable_uncorrectable, #enabled_line?, #file_name_matches_any?, #find_message, #find_severity, #range_for_original, #range_from_node_or_range,

Actually private methods.


::RuboCop::Cop::AutocorrectLogic - Included

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

This class inherits a constructor from RuboCop::Cop::Base

Instance Attribute Details

#require_parentheses_for_method_chain?Boolean (readonly, private)

[ GitHub ]

# File 'lib/rubocop/cop/lint/ambiguous_range.rb', line 99

def require_parentheses_for_method_chain?

Instance Method Details

#acceptable?(node) ⇒ Boolean (private)

[ GitHub ]

# File 'lib/rubocop/cop/lint/ambiguous_range.rb', line 82

def acceptable?(node)
  node.begin_type? ||
    node.literal? ||
    node.variable? || node.const_type? || node.self_type? ||
    (node.call_type? && acceptable_call?(node))

#acceptable_call?(node) ⇒ Boolean (private)

[ GitHub ]

# File 'lib/rubocop/cop/lint/ambiguous_range.rb', line 89

def acceptable_call?(node)
  return true if node.unary_operation?

  # Require parentheses when making a method call on a literal
  # to avoid the ambiguity of `1..2.to_a`.
  return false if node.receiver&.basic_literal?

  require_parentheses_for_method_chain? || node.receiver.nil?

#each_boundary(range) {|range.begin| ... } (private)


  • (range.begin)
[ GitHub ]

# File 'lib/rubocop/cop/lint/ambiguous_range.rb', line 77

def each_boundary(range)
  yield range.begin if range.begin
  yield range.end if range.end


Alias for #on_irange.

[ GitHub ]

# File 'lib/rubocop/cop/lint/ambiguous_range.rb', line 73

alias on_erange on_irange

#on_irange(node) Also known as: #on_erange

[ GitHub ]

# File 'lib/rubocop/cop/lint/ambiguous_range.rb', line 64

def on_irange(node)
  each_boundary(node) do |boundary|
    next if acceptable?(boundary)

    add_offense(boundary) do |corrector|
      corrector.wrap(boundary, '(', ')')