class Molinillo::Resolver::Resolution

def attempt_to_activate
  debug(depth) { 'Attempting to activate ' + possibility.to_s }
  existing_vertex = activated.vertex_named(name)
  if existing_vertex.payload
    debug(depth) { "Found existing spec (#{existing_vertex.payload})" }
    attempt_to_filter_existing_spec(existing_vertex)
  else
    latest = possibility.latest_version
    possibility.possibilities.select! do |possibility|
      requirement_satisfied_by?(requirement, activated, possibility)
    end
    if possibility.latest_version.nil?
      # ensure there's a possibility for better error messages
      possibility.possibilities << latest if latest
      create_conflict
      unwind_for_conflict
    else
      activate_new_spec
    end
  end
end