class RuboCop::Cop::Style::IdenticalConditionalBranches

end
do_z
do_x
else
# nothing
in 2
do_y
do_x
in 1
case foo
# good
end
do_x
else
do_x
in 2
do_x
in 1
case foo
# bad
end
do_z
do_x
else
# nothing
when 2
do_y
do_x
when 1
case foo
# good
end
do_x
else
do_x
when 2
do_x
when 1
case foo
# bad
end
do_y
else
do_x
if condition
do_z
# good
end
do_y
do_z
else
do_x
do_z
if condition
# bad
do_z
end
do_y
else
do_x
if condition
# good
end
do_z
do_y
else
do_z
do_x
if condition
# bad
@example
`method_that_modifies_global_state`, which changes the behaviour of the program.
In this example, ‘method_that_relies_on_global_state` will be moved before
—-
end
bar # 3
method_that_relies_on_global_state # 2
else
foo # 3
method_that_relies_on_global_state # 2
if method_that_modifies_global_state # 1
—-
[source,ruby]

may change the behaviour of the code. For example:
Auto-correction is unsafe because changing the order of method invocations
@safety
in a future major RuboCop release.
checks for duplicated conditional branches. The name will probably be changed
NOTE: The cop is poorly named and some people might think that it actually
be placed outside the conditional expression - before or after it.
each branch of a conditional expression. Such expressions should normally
This cop checks for identical expressions at the beginning or end of

def check_branches(node, branches) 

def check_branches(node, branches)
  # return if any branch is empty. An empty branch can be an `if`
  # without an `else` or a branch that contains only comments.
  return if branches.any?(&:nil?)
  tails = branches.map { |branch| tail(branch) }
  check_expressions(node, tails, :after_condition) if duplicated_expressions?(node, tails)
  heads = branches.map { |branch| head(branch) }
  check_expressions(node, heads, :before_condition) if duplicated_expressions?(node, heads)
end

def check_expressions(node, expressions, insert_position) # rubocop:disable Metrics/MethodLength

rubocop:disable Metrics/MethodLength 
def check_expressions(node, expressions, insert_position) # rubocop:disable Metrics/MethodLength
  inserted_expression = false
  expressions.each do |expression|
    add_offense(expression) do |corrector|
      next if node.if_type? && node.ternary?
      range = range_by_whole_lines(expression.source_range, include_final_newline: true)
      corrector.remove(range)
      next if inserted_expression
      if insert_position == :after_condition
        corrector.insert_after(node, "\n#{expression.source}")
      else
        corrector.insert_before(node, "#{expression.source}\n")
      end
      inserted_expression = true
    end
  end
end

def duplicated_expressions?(node, expressions) 

def duplicated_expressions?(node, expressions)
  unique_expressions = expressions.uniq
  return false unless expressions.size >= 1 && unique_expressions.one?
  unique_expression = unique_expressions.first
  return true unless unique_expression.assignment?
  lhs = unique_expression.child_nodes.first
  node.condition.child_nodes.none? { |n| n.source == lhs.source if n.variable? }
end

def expand_elses(branch)

need to recursively iterate over all `else` branches.
`elsif` branches show up in the if node as nested `else` branches. We 
def expand_elses(branch)
  if branch.nil?
    [nil]
  elsif branch.if_type?
    _condition, elsif_branch, else_branch = *branch
    expand_elses(else_branch).unshift(elsif_branch)
  else
    [branch]
  end
end

def head(node) 

def head(node)
  node.begin_type? ? node.children.first : node
end

def message(node) 

def message(node)
  format(MSG, source: node.source)
end

def on_case(node) 

def on_case(node)
  return unless node.else? && node.else_branch
  branches = node.when_branches.map(&:body).push(node.else_branch)
  check_branches(node, branches)
end

def on_case_match(node) 

def on_case_match(node)
  return unless node.else? && node.else_branch
  branches = node.in_pattern_branches.map(&:body).push(node.else_branch)
  check_branches(node, branches)
end

def on_if(node) 

def on_if(node)
  return if node.elsif?
  branches = expand_elses(node.else_branch).unshift(node.if_branch)
  check_branches(node, branches)
end

def tail(node) 

def tail(node)
  node.begin_type? ? node.children.last : node
end