class RuboCop::Cop::Lint::UselessAssignment

end
do_something(some_var)
some_var = 1
def some_method
# good
@example
end
do_something
some_var = 1
def some_method
# bad
@example
rescue, ensure, etc.
reassignments and properly handles varied cases such as branch, loop,
Currently this cop has advanced logic that detects unreferenced
assigned but unused variable - foo
The basic idea for this cop was from the warning of ‘ruby -cw`:
scope.
This cop checks for every useless assignment to local variable in every

def after_leaving_scope(scope, _variable_table) 

def after_leaving_scope(scope, _variable_table)
  scope.variables.each_value do |variable|
    check_for_unused_assignments(variable)
  end
end

def check_for_unused_assignments(variable) 

def check_for_unused_assignments(variable)
  return if variable.should_be_unused?
  variable.assignments.each do |assignment|
    next if assignment.used?
    message = message_for_useless_assignment(assignment)
    location = if assignment.regexp_named_capture?
                 assignment.node.children.first.source_range
               else
                 assignment.node.loc.name
               end
    add_offense(nil, location: location, message: message)
  end
end

def collect_variable_like_names(scope) 

def collect_variable_like_names(scope)
  names = scope.each_node.with_object(Set.new) do |node, set|
    if variable_like_method_invocation?(node)
      _receiver, method_name, = *node
      set << method_name
    end
  end
  variable_names = scope.variables.each_value.map(&:name)
  names.merge(variable_names)
end

def join_force?(force_class) 

def join_force?(force_class)
  force_class == VariableForce
end

def message_for_useless_assignment(assignment) 

def message_for_useless_assignment(assignment)
  variable = assignment.variable
  format(MSG, variable: variable.name) +
    message_specification(assignment, variable).to_s
end

def message_specification(assignment, variable) 

def message_specification(assignment, variable)
  if assignment.multiple_assignment?
    multiple_assignment_message(variable.name)
  elsif assignment.operator_assignment?
    operator_assignment_message(variable.scope, assignment)
  else
    similar_name_message(variable)
  end
end

def multiple_assignment_message(variable_name) 

def multiple_assignment_message(variable_name)
  " Use `_` or `_#{variable_name}` as a variable name to indicate " \
    "that it won't be used."
end

def operator_assignment_message(scope, assignment) 

def operator_assignment_message(scope, assignment)
  return_value_node = return_value_node_of_scope(scope)
  return unless assignment.meta_assignment_node
                          .equal?(return_value_node)
  " Use `#{assignment.operator.sub(/=$/, '')}` " \
  "instead of `#{assignment.operator}`."
end

def return_value_node_of_scope(scope)

TODO: More precise handling (rescue, ensure, nested begin, etc.) 
def return_value_node_of_scope(scope)
  body_node = scope.body_node
  if body_node.begin_type?
    body_node.children.last
  else
    body_node
  end
end

def similar_name_message(variable) 

def similar_name_message(variable)
  similar_name = find_similar_name(variable.name, variable.scope)
  " Did you mean `#{similar_name}`?" if similar_name
end

def variable_like_method_invocation?(node) 

def variable_like_method_invocation?(node)
  return false unless node.send_type?
  receiver, _method_name, *args = *node
  receiver.nil? && args.empty?
end