rustc_builtin_macros/deriving/cmp/
ord.rs

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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    // Builds:
48    //
49    // match ::core::cmp::Ord::cmp(&self.x, &other.x) {
50    //     ::std::cmp::Ordering::Equal =>
51    //         ::core::cmp::Ord::cmp(&self.y, &other.y),
52    //     cmp => cmp,
53    // }
54    let expr = cs_fold(
55        // foldr nests the if-elses correctly, leaving the first field
56        // as the outermost one, and the last as the innermost.
57        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}
rustc_builtin_macros/deriving/cmp/ord.rs

rustc_builtin_macros/deriving/cmp/
ord.rs
