Function is_subclass_of

src/completion/variable/forward_walk.rs:2013–2043

Check whether `child` is a subclass (direct or transitive) of `parent` by walking the inheritance chain via the class loader. Returns `false` if either class cannot be loaded or if there is no inheritance relationship. Limits the chain walk to 20 steps to avoid infinite loops on cyclic hierarchies.

(
    child: &str,
    parent: &str,
    class_loader: &dyn Fn(&str) -> Option<Arc<ClassInfo>>,
)

/// no inheritance relationship.  Limits the chain walk to 20 steps
/// to avoid infinite loops on cyclic hierarchies.
fn is_subclass_of(
    child: &str,
    parent: &str,
    class_loader: &dyn Fn(&str) -> Option<Arc<ClassInfo>>,
) -> bool {
    if child.eq_ignore_ascii_case(parent) {
        return false; // same class, not a subclass
    }
    let mut current = child.to_string();
    for _ in 0..20 {
        let cls = match class_loader(&current) {
            Some(c) => c,
            None => return false,
        };
        // Check implemented interfaces at every level.
        for iface in &cls.interfaces {
            if iface.as_str().eq_ignore_ascii_case(parent) {
                return true;
            }
        }
        if let Some(ref p) = cls.parent_class {
            if p.as_str().eq_ignore_ascii_case(parent) {
                return true;
            }
            current = p.to_string();
        } else {
            return false;
        }
    }
    false
}

/// Context for the forward walk.
///