Function arg_check_parts 

#[doc(hidden)]
pub fn arg_check_parts(
    message: &str,
    param: &str,
    crate_class: &[&str],
) -> ErrParts

The parts of an argument check that failed in Rust after the conversion: #[miniextendr(no_na)] on a reading marker (AsNumeric*, AsCharacter*) whose converted value holds an NA that R’s anyNA() did not see (the hidden TryFromSexp::__mx_has_na says so), or on an Either, which has no R guard, an NA the arm taken refuses (TryFromSexp::__mx_input_has_na).

The shape is the R guard’s (.miniextendr_arg_error): message as given (the macro writes '<p>' must not be NA or the author’s own message), the classes crate_class (the crate’s conversion_error_class), and param as the only data field, e$param. No rust_type: the R guard has none, and the two paths raise one condition.