Invariant for default construction

[Walter Bright via Digitalmars-d]

On 11/17/2014 11:58 PM, Rainer Schuetze wrote:
> I remember having an invariant on a tree structure checking consistency by
> verifying the children and parent references. This crashed when adding a
> destructor. With the proposed change it will always crash.
>
> The problem is that the destructors of the tree nodes are called in arbitrary
> order when they are collected by the GC. Class instances are also made invalid
> after calling the destructor (the vtbl is zeroed).
>
> I wonder if
>
> - such invariants are invalid,
> - the GC should bypass the invariant when calling the destructor
> - or we should never call the invariant with the destructor?

Invariants should be checking the state of the object that it owns, not other 
objects. I would consider such an invariant invalid.