rustc_builtin_macros/deriving/cmp/
eq.rs

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1use rustc_ast::{self as ast, MetaItem};
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: 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: vec![MethodDef {
29            name: sym::assert_receiver_is_total_eq,
30            generics: Bounds::empty(),
31            explicit_self: true,
32            nonself_args: vec![],
33            ret_ty: Unit,
34            attributes: thin_vec![
35                cx.attr_word(sym::inline, span),
36                cx.attr_nested_word(sym::doc, sym::hidden, span),
37                cx.attr_nested_word(sym::coverage, sym::off, span)
38            ],
39            fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
40            combine_substructure: combine_substructure(Box::new(|a, b, c| {
41                cs_total_eq_assert(a, b, c)
42            })),
43        }],
44        associated_types: Vec::new(),
45        is_const,
46    };
47    trait_def.expand_ext(cx, mitem, item, push, true)
48}
49
50fn cs_total_eq_assert(
51    cx: &ExtCtxt<'_>,
52    trait_span: Span,
53    substr: &Substructure<'_>,
54) -> BlockOrExpr {
55    let mut stmts = ThinVec::new();
56    let mut seen_type_names = FxHashSet::default();
57    let mut process_variant = |variant: &ast::VariantData| {
58        for field in variant.fields() {
59            // This basic redundancy checking only prevents duplication of
60            // assertions like `AssertParamIsEq<Foo>` where the type is a
61            // simple name. That's enough to get a lot of cases, though.
62            if let Some(name) = field.ty.kind.is_simple_path()
63                && !seen_type_names.insert(name)
64            {
65                // Already produced an assertion for this type.
66            } else {
67                // let _: AssertParamIsEq<FieldTy>;
68                super::assert_ty_bounds(
69                    cx,
70                    &mut stmts,
71                    field.ty.clone(),
72                    field.span,
73                    &[sym::cmp, sym::AssertParamIsEq],
74                );
75            }
76        }
77    };
78
79    match *substr.fields {
80        StaticStruct(vdata, ..) => {
81            process_variant(vdata);
82        }
83        StaticEnum(enum_def, ..) => {
84            for variant in &enum_def.variants {
85                process_variant(&variant.data);
86            }
87        }
88        _ => cx.dcx().span_bug(trait_span, "unexpected substructure in `derive(Eq)`"),
89    }
90    BlockOrExpr::new_stmts(stmts)
91}
rustc_builtin_macros/deriving/cmp/eq.rs

rustc_builtin_macros/deriving/cmp/
eq.rs
