pub(crate) fn declared_formal_problem(formal: &str) -> Option<String>Expand description
Why formal can’t be a declared formal, or None when it can: it must be
a syntactic R name (crate::naming::is_syntactic_r_name: letters,
digits, . and _, not starting with a digit, _ or . and a digit, and
not a reserved word), not ... or ..1 (R’s dots), and none of the names
the generated wrapper binds itself (FRAMEWORK_FORMALS,
FRAMEWORK_FORMAL_PREFIXES).