Default initialization of structs?

[Kagamin via Digitalmars-d-learn]

On Friday, 17 June 2016 at 12:31:33 UTC, David Nadlinger wrote:
> Structs cannot have a default constructor; .init is required to 
> be a valid state (unless you @disable default construction).

Except for nested structs :) They have the default constructor 
and their .init is not a valid state: has null context pointer.