rustc_builtin_macros/deriving/cmp/
ord.rs
1use rustc_ast::MetaItem;
2use rustc_expand::base::{Annotatable, ExtCtxt};
3use rustc_span::{Ident, Span, sym};
4use thin_vec::thin_vec;
5
6use crate::deriving::generic::ty::*;
7use crate::deriving::generic::*;
8use crate::deriving::path_std;
9
10pub(crate) fn expand_deriving_ord(
11 cx: &ExtCtxt<'_>,
12 span: Span,
13 mitem: &MetaItem,
14 item: &Annotatable,
15 push: &mut dyn FnMut(Annotatable),
16 is_const: bool,
17) {
18 let trait_def = TraitDef {
19 span,
20 path: path_std!(cmp::Ord),
21 skip_path_as_bound: false,
22 needs_copy_as_bound_if_packed: true,
23 additional_bounds: Vec::new(),
24 supports_unions: false,
25 methods: vec![MethodDef {
26 name: sym::cmp,
27 generics: Bounds::empty(),
28 explicit_self: true,
29 nonself_args: vec![(self_ref(), sym::other)],
30 ret_ty: Path(path_std!(cmp::Ordering)),
31 attributes: thin_vec![cx.attr_word(sym::inline, span)],
32 fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
33 combine_substructure: combine_substructure(Box::new(|a, b, c| cs_cmp(a, b, c))),
34 }],
35 associated_types: Vec::new(),
36 is_const,
37 };
38
39 trait_def.expand(cx, mitem, item, push)
40}
41
42pub(crate) fn cs_cmp(cx: &ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
43 let test_id = Ident::new(sym::cmp, span);
44 let equal_path = cx.path_global(span, cx.std_path(&[sym::cmp, sym::Ordering, sym::Equal]));
45 let cmp_path = cx.std_path(&[sym::cmp, sym::Ord, sym::cmp]);
46
47 let expr = cs_fold(
55 false,
58 cx,
59 span,
60 substr,
61 |cx, fold| match fold {
62 CsFold::Single(field) => {
63 let [other_expr] = &field.other_selflike_exprs[..] else {
64 cx.dcx().span_bug(field.span, "not exactly 2 arguments in `derive(Ord)`");
65 };
66 let args = thin_vec![field.self_expr.clone(), other_expr.clone()];
67 cx.expr_call_global(field.span, cmp_path.clone(), args)
68 }
69 CsFold::Combine(span, expr1, expr2) => {
70 let eq_arm = cx.arm(span, cx.pat_path(span, equal_path.clone()), expr1);
71 let neq_arm =
72 cx.arm(span, cx.pat_ident(span, test_id), cx.expr_ident(span, test_id));
73 cx.expr_match(span, expr2, thin_vec![eq_arm, neq_arm])
74 }
75 CsFold::Fieldless => cx.expr_path(equal_path.clone()),
76 },
77 );
78 BlockOrExpr::new_expr(expr)
79}