Function gen_layout_ctx_expr_inefficient 

pub(crate) fn gen_layout_ctx_expr_inefficient(
    ty: &Type,
    is_manual_slot: bool,
    _slot_const_ref: TokenStream,
    offset_const_ref: TokenStream,
    _prev_slot_const_ref: Option<TokenStream>,
    _next_slot_const_ref: Option<TokenStream>,
) -> TokenStream

Generate a LayoutCtx expression for accessing a field.

Despite we could deterministically know if a field shares its slot with a neighbour, we treat all primitive types as packable for backward-compatibility reasons.