Function nested_type_is_emitted 

pub fn nested_type_is_emitted(
    analyzed: &AnalyzedQuery,
    supported: &[NestedStructDef],
    prefix: &str,
    sql_name: &str,
) -> bool

Whether sql_name is reachable from a nested-aggregate struct the backend actually emitted a definition for.

The supported filter keeps degraded output self-contained: a type reachable only through a nested struct rewritten to json or json_array must not be emitted at all.