DDSXTY — Mutable structures with an empty intersection should not be considered assignable

The type assignability rules for structure types (section 7.2.4.5, Aggregation Types) allow mutable types to be assigned in either direction, so long as there are no name, ID, or type conflicts among the types’ members. Unfortunately, these rules permit a degenerate case: two mutable types having no key members and no members in common will have no conflicts, and therefore will be considered assignable. However, readers will always observe every sample to have all default/empty contents.
Resolution:
Add an additional rule to the assignability determination to require that at least one member is in common.

Add an additional rule to the assignability determination to require that at least
one member is in common.