private Stream<MemberShape> newRequiredMembers(Differences differences) {
        return differences.changedShapes(StructureShape.class)
                .flatMap(change -> change.getNewShape()
                        .members()
                        .stream()
                        .filter(newMember -> newMember.hasTrait(RequiredTrait.ID)
                                && !newMember.hasTrait(DefaultTrait.ID)
                                // Members that did not exist before
                                && change.getOldShape().getAllMembers().get(newMember.getMemberName()) == null));
    }
Validates that no members are newly created with the required trait
(but no default trait) in existing structures.
smithy-diff/src/main/java/software/amazon/smithy/diff/evaluators/AddedRequiredMember.java