Function object_macro_replacement_fields 

pub fn object_macro_replacement_fields(
    replacement: &str,
) -> Vec<MacroReplacementField>

Recover direct fields hidden in an object-like macro replacement.

A field-list macro is valid in more than one owner, so this helper returns only the declaration-shaped children of the synthetic field list. Nested aggregate promotion remains the owner’s normal structured aggregate logic; treating nested members as direct fields here would leak them across owners.