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// 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();
  }
}