module SimpleCov::Combine::BranchesCombiner

def combine(coverage_a, coverage_b)
  merged = {} #: Hash[untyped, [untyped, Hash[untyped, untyped]]]
  combined = [coverage_a, coverage_b].each_with_object(merged) do |coverage, memo|
    coverage.each do |condition, branches_inside|
      condition_key = tuple_identity(condition)
      condition_tuple, merged_branches = memo[condition_key] ||= [condition, {}]
      merge_branches(merged_branches, branches_inside)
      memo[condition_key] = [condition_tuple, merged_branches]
    end
  end
  combined.values.to_h { |condition, branches| [condition, branches.values.to_h] }
end