BUG: Bounds doesn't work as auto-implemented properties (2020.1.11f1)

Code (CSharp):

1. public Bounds someBounds { get; private set; }
2.  
3. ...
4.  
5. // Wont work
6. someBounds.Encapsulate(otherBoundsOrPoint);
7.  
8. // You will have to
9. temp = someBounds;
10. temp.Encapsulate(otherBoundsOrPoint);
11. someBounds = temp;
12.  
13. // or decalre bounds as
14. Bounds _someBoundsInternal;
15. public Bounds someBounds => _someBoundsInternal;

This one made made me cry a bit ...

As far I remember this used to work, or it always broken like this and I never stumble upon this bug ?!?!?

 

It's the same issue as affects any property that returns a struct: properties are actually a pair of get/set functions masquerading as a variable, and changing variables on the copy you receive from the "get" will not affect the main object. So when you call this:

Code (csharp):

1. someBounds.Encapsulate(other);

What the compiler sees is this:

Code (csharp):

1. GetSomeBounds().Encapsulate(other);

So GetSomeBounds() returns a copy of the Bounds object (because structs are passed by value), you call Encapsulate which affects that returned copy, but then that copy is lost to the ether because nothing was there to catch it.

This is the same reason that

transform.position.x = 5f;

doesn't work. position is a property, the "get" accessor generates/returns a copy of the Vector3 struct, and when .x is changed that doesn't apply to the source.

It's possible that:
1) you may be remembering using a public member this way that WASN'T a property; that wouldn't have this limitation.
2) you may have used Encapsulate way back in the days of Javascript, where this would I think actually work. JS had some sort of weird convenience hack that allowed transform.position.x = 5; to work, and I assume the same would be true of other properties
3) There's a very tiny chance that a long long time ago, Bounds might have been a class and not a struct, and this logic would work fine on a class. (I looked back as far as the docs have history, which is Unity 5.2, and it's a struct then, so it'd have been >5 years ago if this is the case. And I don't think it is)

 

Oh, makes sense thanks!