Prevent stack overflow in Attribute.cs

[leotsarev]

fixes #35784

[teo-tsirpanis]

The comment is incorrect, but I'm not sure whether behavior needs to change. An Attribute containing an Attribute does not necessarily lead to stack overflows; it does only if there is a cycle, and if there is, a custom override of the Equals method looks better.

Are there any real-world examples that would need this fix?

[leotsarev]

Real life example was from my code (see original bug).

[leotsarev]

I agree that custom Equals override should be better, but I think that framework should show correct error.

[leotsarev]

I finally able to formulate why I think that need to be changed.
Debug.Assert should prevent us from errors in private code. If public endpoint could lead to some failure, Debug.Assert is not enough and we need to throw exception here.

[jkotas]

There are many ways the default implementation of Equals for ValueTypes or Attributes can lead to an infinite recursion. It is not practical to prevent it.

We should delete the Debug.Assert(thisValue is not Attribute); from this code since it is an invalid assertion.

[leotsarev]

@jkotas as you wish