class Unparser::AST::LocalVariableScope

def first_assignment?(node)
  name = node.children.first
  match(node) do |current, before|
    current.include?(name) && !before.include?(name)
  end
end

def first_assignment_in?(left, right)
  condition_reads = AST.local_variable_reads(right)
  candidates = AST.local_variable_assignments(left).select do |node|
    condition_reads.include?(node.children.first)
  end
  candidates.any?(&public_method(:first_assignment?))
end

def initialize(*arguments)
  super
  items = []
  LocalVariableScopeEnumerator.each(
    node:  node,
    stack: static_local_variables.dup
  ) { |*scope| items << scope }
  @items = items
end

def local_variable_defined_for_node?(node, name)
  match(node) do |current|
    current.include?(name)
  end
end

def local_variables_for_node(needle)
  @items.each do |node, current|
    return current if node.equal?(needle)
  end
  Set.new
end

def match(needle)
  @items.each do |node, current, before|
    return yield(current, before) if node.equal?(needle)
  end
end