The all-zero, VM defined, default value has been removed from the value class model for JEP 401. Its implementation, and all optimization based on its existence have to be removed. This removal also impact any API that was assuming the existence of such value. The @ImplicitlyConstructible annotation, signaling that the VM was allowed to use a default value for an annotated value class, has to be removed as well.
Tests using @NullRestricted annotated fields must be re-written to add the @Strict annotation and ensure the field is properly initialized with explicitly Java code according to the strict fields rules.