Function gen_collision_check_fn 

pub(crate) fn gen_collision_check_fn(
    idx: usize,
    field: &LayoutField<'_>,
    all_fields: &[LayoutField<'_>],
) -> Option<(Ident, TokenStream)>

Generate collision detection debug assertions for a field against all other fields.

This function generates runtime checks that verify storage slots don’t overlap. Only manual slot assignments are checked, as auto-assigned slots are guaranteed not to collide by the allocation algorithm.