1 use crate::deriving::generic::ty::*;
2 use crate::deriving::generic::*;
3 use crate::deriving::path_std;
4 use rustc_ast::MetaItem;
5 use rustc_expand::base::{Annotatable, ExtCtxt};
6 use rustc_span::symbol::{sym, Ident};
8 use thin_vec::thin_vec;
10 pub fn expand_deriving_ord(
15 push: &mut dyn FnMut(Annotatable),
18 let attrs = thin_vec![cx.attr_word(sym::inline, span)];
19 let trait_def = TraitDef {
21 path: path_std!(cmp::Ord),
22 skip_path_as_bound: false,
23 needs_copy_as_bound_if_packed: true,
24 additional_bounds: Vec::new(),
25 supports_unions: false,
26 methods: vec![MethodDef {
28 generics: Bounds::empty(),
30 nonself_args: vec![(self_ref(), sym::other)],
31 ret_ty: Path(path_std!(cmp::Ordering)),
33 fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
34 combine_substructure: combine_substructure(Box::new(|a, b, c| cs_cmp(a, b, c))),
36 associated_types: Vec::new(),
40 trait_def.expand(cx, mitem, item, push)
43 pub fn cs_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
44 let test_id = Ident::new(sym::cmp, span);
45 let equal_path = cx.path_global(span, cx.std_path(&[sym::cmp, sym::Ordering, sym::Equal]));
46 let cmp_path = cx.std_path(&[sym::cmp, sym::Ord, sym::cmp]);
50 // match ::core::cmp::Ord::cmp(&self.x, &other.x) {
51 // ::std::cmp::Ordering::Equal =>
52 // ::core::cmp::Ord::cmp(&self.y, &other.y),
56 // foldr nests the if-elses correctly, leaving the first field
57 // as the outermost one, and the last as the innermost.
62 |cx, fold| match fold {
63 CsFold::Single(field) => {
64 let [other_expr] = &field.other_selflike_exprs[..] else {
65 cx.span_bug(field.span, "not exactly 2 arguments in `derive(Ord)`");
67 let args = vec![field.self_expr.clone(), other_expr.clone()];
68 cx.expr_call_global(field.span, cmp_path.clone(), args)
70 CsFold::Combine(span, expr1, expr2) => {
71 let eq_arm = cx.arm(span, cx.pat_path(span, equal_path.clone()), expr1);
73 cx.arm(span, cx.pat_ident(span, test_id), cx.expr_ident(span, test_id));
74 cx.expr_match(span, expr2, vec![eq_arm, neq_arm])
76 CsFold::Fieldless => cx.expr_path(equal_path.clone()),
79 BlockOrExpr::new_expr(expr)