// TODO: Store Class AND Type

// Describes a value during script optimization/type inference.

// In the best case, the exact value is known.

// Next best case is we're knowing its precise type (value of object.getClass()).

// Third best case is we're knowing it's castable to a certain type.

// A completely unknown value is described simply by "new LASValueDescriptor".

persistable sclass LASValueDescriptor {

  bool knownValue() { false; }

  O value() { null; }

  Type type() { ret javaClass(); }

  Class javaClass() { null; }

  bool javaClassIsExact() { false; }

  bool canBeNull() { true; }

  bool canFail() { false; }

  bool willFail() { false; }

  srecord Exact(Class c, bool canBeNull) > LASValueDescriptor {

    Class javaClass() { ret c; }

    bool javaClassIsExact() { true; }

    bool canBeNull() { ret canBeNull; }

  }

  srecord NonExact(Class c, bool canBeNull) > LASValueDescriptor {

    Class javaClass() { ret c; }

    bool javaClassIsExact() { false; }

    bool canBeNull() { ret canBeNull; }

  }

  // only returns a type(), not a javaClass()

  // (e.g. for LAS classes still being defined)

  srecord NonExactType(Type type, bool canBeNull) > LASValueDescriptor {

    Type type() { ret type; }

    bool javaClassIsExact() { false; }

    bool canBeNull() { ret canBeNull; }

  }

  static LASValueDescriptor nonExactCanBeNull(Type c) {

    ret new NonExact(typeToClass(c), true);

  }

  srecord KnownValue(O value) > LASValueDescriptor {

    bool knownValue() { true; }

    O value() { ret value; }

    Class javaClass() { ret value?.getClass(); }

    bool javaClassIsExact() { ret value != null; }

    bool canBeNull() { ret value == null; }

  }

  // Indicates an exception can be thrown instead of returning a value.

  // Probably we don't need this.

  sclass WillFail > LASValueDescriptor {

    bool canFail() { true; }

    bool willFail() { true; }

  }

  static LASValueDescriptor fromClass(Class c) {

    ret new NonExact(c, true);

  }

  static LASValueDescriptor fromType(Type type) {

    ret new NonExact(typeToClass(type), true);

  }

  toString {

    ret "LASValueDescriptor " + javaClass();

  }

}