Function cpp_comparable_parameter_shapes 

pub fn cpp_comparable_parameter_shapes<'tree>(
    function_declarator: Node<'tree>,
    source: &str,
    ancestry: &ParentIndex<'tree>,
) -> Option<Vec<CppComparableSlot>>

The comparable shape of each invocation parameter, in declaration order.

The result is index-parallel with cpp_callable_parameter_type_identities; a parameter that admits no comparable shape is CppComparableSlot::Unstructured, which a comparison must treat as evidence of nothing rather than as agreement. Outer None means the grammar did not prove the parameter list.