rustc_builtin_macros/deriving/
eq.rs

1use rustc_ast::{self as ast, Safety};
2use rustc_data_structures::fx::FxHashSet;
3use rustc_expand::base::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    item: &ast::Item,
15    push: &mut dyn FnMut(Box<ast::Item>),
16    is_const: bool,
17) {
18    let span = cx.with_def_site_ctxt(span);
19
20    let trait_def = TraitDef {
21        span,
22        path: generic::ty::new_path(cx, span, { &[sym::cmp, sym::Eq] }, &[])path_std!(cx, span, cmp::Eq),
23        skip_path_as_bound: false,
24        needs_copy_as_bound_if_packed: true,
25        additional_bounds: SmallVec::new(),
26        supports_unions: true,
27        methods: {
    let count = 0usize + 1usize;
    let mut vec = ::smallvec::SmallVec::new();
    if count <= vec.inline_size() {
        vec.push(MethodDef {
                name: sym::assert_fields_are_eq,
                generics: cx.empty_generics(span),
                explicit_self: true,
                nonself_args: ::smallvec::SmallVec::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(cs_total_eq_assert),
            });
        vec
    } else {
        ::smallvec::SmallVec::from_vec(::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: cx.empty_generics(span),
                                explicit_self: true,
                                nonself_args: ::smallvec::SmallVec::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(cs_total_eq_assert),
                            }])))
    }
}smallvec![MethodDef {
28            name: sym::assert_fields_are_eq,
29            generics: cx.empty_generics(span),
30            explicit_self: true,
31            nonself_args: smallvec![],
32            ret_ty: Unit,
33            attributes: thin_vec![
34                // This method will never be called, so doing codegen etc. for it is unnecessary.
35                // We prevent this by adding `#[inline]`, which improves compile-time.
36                cx.attr_word(sym::inline, span),
37                cx.attr_nested_word(sym::doc, sym::hidden, span),
38                cx.attr_nested_word(sym::coverage, sym::off, span),
39            ],
40            fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
41            combine_substructure: combine_substructure(cs_total_eq_assert),
42        }],
43        associated_types: SmallVec::new(),
44        is_const,
45        safety: Safety::Default,
46        document: true,
47    };
48    trait_def.expand_ext(cx, item, push, true)
49}
50
51fn cs_total_eq_assert(cx: &ExtCtxt<'_>, trait_span: Span, substr: Substructure<'_>) -> BlockOrExpr {
52    let mut stmts = ThinVec::new();
53    let mut seen_type_names = FxHashSet::default();
54    let mut process_variant = |variant: &ast::VariantData| {
55        for field in variant.fields() {
56            // This basic redundancy checking only prevents duplication of
57            // assertions like `AssertParamIsEq<Foo>` where the type is a
58            // simple name. That's enough to get a lot of cases, though.
59            if let Some(name) = field.ty.kind.is_simple_path()
60                && !seen_type_names.insert(name)
61            {
62                // Already produced an assertion for this type.
63            } else {
64                // let _: AssertParamIsEq<FieldTy>;
65                super::assert_ty_bounds(
66                    cx,
67                    &mut stmts,
68                    field.ty.clone(),
69                    field.span,
70                    &[sym::cmp, sym::AssertParamIsEq],
71                );
72            }
73        }
74    };
75
76    match substr {
77        StaticStruct(vdata, ..) => {
78            process_variant(vdata);
79        }
80        StaticEnum(enum_def, ..) => {
81            for variant in &enum_def.variants {
82                process_variant(&variant.data);
83            }
84        }
85        _ => cx.dcx().span_bug(trait_span, "unexpected substructure in `derive(Eq)`"),
86    }
87    BlockOrExpr::new_stmts(stmts)
88}
rustc_builtin_macros/deriving/eq.rs

rustc_builtin_macros/deriving/
eq.rs
