src/Pure/Thy/thy_load.scala

clarified fulfill_norm_proof: no join_thms yet;
clarified priority of fulfill_proof_future, which is followed by explicit join_thms;
explicit Thm.future_body_of without join yet;
tuned Thm.future_result: join_promises without fulfill_norm_proof;

/*  Title:      Pure/Thy/thy_load.scala
    Author:     Makarius

Loading files that contribute to a theory.
*/

package isabelle

abstract class Thy_Load
{
  def is_loaded(name: String): Boolean

  def check_thy(dir: Path, name: String): (String, Thy_Header)
}