in core/src/main/java/org/apache/jsieve/SieveValidationVisitor.java [159:171]
private void comparatorNameArgument(ASTstring node) throws SieveException {
final Object value = node.getValue();
if (value != null && value instanceof String) {
final String name = (String) value;
// Comparators must either be declared (either implicitly or explicitly)
if (!comparatorManager.isImplicitlyDeclared(name)) {
if (!declaredComparators.contains(name)) {
// TODO: replace with better exception
throw new SieveException("Comparator must be explicitly declared in a require statement.");
}
}
}
}