rustc_builtin_macros/deriving/cmp/
eq.rs

1use rustc_ast::{self as ast, MetaItem, Safety};
2use rustc_data_structures::fx::FxHashSet;
3use rustc_expand::base::{Annotatable, ExtCtxt};
4use rustc_span::{Span, sym};
5use thin_vec::{ThinVec, thin_vec};
6
7use crate::deriving::generic::ty::*;
8use crate::deriving::generic::*;
9use crate::deriving::path_std;
10
11pub(crate) fn expand_deriving_eq(
12    cx: &ExtCtxt<'_>,
13    span: Span,
14    mitem: &MetaItem,
15    item: &Annotatable,
16    push: &mut dyn FnMut(Annotatable),
17    is_const: bool,
18) {
19    let span = cx.with_def_site_ctxt(span);
20
21    let trait_def = TraitDef {
22        span,
23        path: generic::ty::Path::new({
        ::alloc::boxed::box_assume_init_into_vec_unsafe(::alloc::intrinsics::write_box_via_move(::alloc::boxed::Box::new_uninit(),
                [sym::cmp, sym::Eq]))
    })path_std!(cmp::Eq),
24        skip_path_as_bound: false,
25        needs_copy_as_bound_if_packed: true,
26        additional_bounds: Vec::new(),
27        supports_unions: true,
28        methods: ::alloc::boxed::box_assume_init_into_vec_unsafe(::alloc::intrinsics::write_box_via_move(::alloc::boxed::Box::new_uninit(),
        [MethodDef {
                    name: sym::assert_fields_are_eq,
                    generics: Bounds::empty(),
                    explicit_self: true,
                    nonself_args: ::alloc::vec::Vec::new(),
                    ret_ty: Unit,
                    attributes: {
                        let len = [(), (), ()].len();
                        let mut vec = ::thin_vec::ThinVec::with_capacity(len);
                        vec.push(cx.attr_word(sym::inline, span));
                        vec.push(cx.attr_nested_word(sym::doc, sym::hidden, span));
                        vec.push(cx.attr_nested_word(sym::coverage, sym::off,
                                span));
                        vec
                    },
                    fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
                    combine_substructure: combine_substructure(Box::new(|a, b,
                                c| { cs_total_eq_assert(a, b, c) })),
                }]))vec![MethodDef {
29            name: sym::assert_fields_are_eq,
30            generics: Bounds::empty(),
31            explicit_self: true,
32            nonself_args: vec![],
33            ret_ty: Unit,
34            attributes: thin_vec![
35                // This method will never be called, so doing codegen etc. for it is unnecessary.
36                // We prevent this by adding `#[inline]`, which improves compile-time.
37                cx.attr_word(sym::inline, span),
38                cx.attr_nested_word(sym::doc, sym::hidden, span),
39                cx.attr_nested_word(sym::coverage, sym::off, span),
40            ],
41            fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
42            combine_substructure: combine_substructure(Box::new(|a, b, c| {
43                cs_total_eq_assert(a, b, c)
44            })),
45        }],
46        associated_types: Vec::new(),
47        is_const,
48        is_staged_api_crate: cx.ecfg.features.staged_api(),
49        safety: Safety::Default,
50        document: true,
51    };
52    trait_def.expand_ext(cx, mitem, item, push, true)
53}
54
55fn cs_total_eq_assert(
56    cx: &ExtCtxt<'_>,
57    trait_span: Span,
58    substr: &Substructure<'_>,
59) -> BlockOrExpr {
60    let mut stmts = ThinVec::new();
61    let mut seen_type_names = FxHashSet::default();
62    let mut process_variant = |variant: &ast::VariantData| {
63        for field in variant.fields() {
64            // This basic redundancy checking only prevents duplication of
65            // assertions like `AssertParamIsEq<Foo>` where the type is a
66            // simple name. That's enough to get a lot of cases, though.
67            if let Some(name) = field.ty.kind.is_simple_path()
68                && !seen_type_names.insert(name)
69            {
70                // Already produced an assertion for this type.
71            } else {
72                // let _: AssertParamIsEq<FieldTy>;
73                super::assert_ty_bounds(
74                    cx,
75                    &mut stmts,
76                    field.ty.clone(),
77                    field.span,
78                    &[sym::cmp, sym::AssertParamIsEq],
79                );
80            }
81        }
82    };
83
84    match *substr.fields {
85        StaticStruct(vdata, ..) => {
86            process_variant(vdata);
87        }
88        StaticEnum(enum_def, ..) => {
89            for variant in &enum_def.variants {
90                process_variant(&variant.data);
91            }
92        }
93        _ => cx.dcx().span_bug(trait_span, "unexpected substructure in `derive(Eq)`"),
94    }
95    BlockOrExpr::new_stmts(stmts)
96}
rustc_builtin_macros/deriving/cmp/eq.rs

rustc_builtin_macros/deriving/cmp/
eq.rs
