static boolean expectedStringToEnumChange(ChangedShape<Shape> diff) {
        // Smithy diff doesn't raise an issue if a string with an enum trait is changed
        // to an enum shape. The enum trait is deprecated and this is a recommended change.
        return diff.getOldShape().hasTrait(EnumTrait.class) && diff.getNewShape().getType() == ShapeType.ENUM;
    }
Creates an ERROR event when the type of a shape changes.
smithy-diff/src/main/java/software/amazon/smithy/diff/evaluators/ChangedShapeType.java