Function find_bridge_field 

pub fn find_bridge_field<'a>(
    func: &FunctionDef,
    types: &'a [TypeDef],
    bridges: &'a [TraitBridgeConfig],
) -> Option<BridgeFieldMatch<'a>>

Find the first function parameter whose IR type carries a bridge field (bind_via = "options_field").

For each function parameter whose IR type is Named(N) or Optional<Named(N)>, look up N in types. If N matches any bridge’s options_type, search its fields for one whose name matches the bridge’s resolved options field (or whose type’s Named alias matches the bridge’s type_alias). Returns the first match.

Bridges configured with bind_via = "function_param" are skipped — those go through find_bridge_param instead.