rustc_builtin_macros/deriving/
hash.rs

1use rustc_ast::{MetaItem, Mutability};
2use rustc_expand::base::{Annotatable, ExtCtxt};
3use rustc_span::{Span, sym};
4use thin_vec::thin_vec;
5
6use crate::deriving::generic::ty::*;
7use crate::deriving::generic::*;
8use crate::deriving::{path_std, pathvec_std};
9
10pub(crate) fn expand_deriving_hash(
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 path = Path::new_(pathvec_std!(hash::Hash), vec![], PathKind::Std);
19
20    let typaram = sym::__H;
21
22    let arg = Path::new_local(typaram);
23    let hash_trait_def = TraitDef {
24        span,
25        path,
26        skip_path_as_bound: false,
27        needs_copy_as_bound_if_packed: true,
28        additional_bounds: Vec::new(),
29        supports_unions: false,
30        methods: vec![MethodDef {
31            name: sym::hash,
32            generics: Bounds { bounds: vec![(typaram, vec![path_std!(hash::Hasher)])] },
33            explicit_self: true,
34            nonself_args: vec![(Ref(Box::new(Path(arg)), Mutability::Mut), sym::state)],
35            ret_ty: Unit,
36            attributes: thin_vec![cx.attr_word(sym::inline, span)],
37            fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
38            combine_substructure: combine_substructure(Box::new(|a, b, c| {
39                hash_substructure(a, b, c)
40            })),
41        }],
42        associated_types: Vec::new(),
43        is_const,
44        is_staged_api_crate: cx.ecfg.features.staged_api(),
45    };
46
47    hash_trait_def.expand(cx, mitem, item, push);
48}
49
50fn hash_substructure(cx: &ExtCtxt<'_>, trait_span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
51    let [state_expr] = substr.nonselflike_args else {
52        cx.dcx().span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`");
53    };
54    let call_hash = |span, expr| {
55        let hash_path = {
56            let strs = cx.std_path(&[sym::hash, sym::Hash, sym::hash]);
57
58            cx.expr_path(cx.path_global(span, strs))
59        };
60        let expr = cx.expr_call(span, hash_path, thin_vec![expr, state_expr.clone()]);
61        cx.stmt_expr(expr)
62    };
63
64    let (stmts, match_expr) = match substr.fields {
65        Struct(_, fields) | EnumMatching(.., fields) => {
66            let stmts =
67                fields.iter().map(|field| call_hash(field.span, field.self_expr.clone())).collect();
68            (stmts, None)
69        }
70        EnumDiscr(discr_field, match_expr) => {
71            assert!(discr_field.other_selflike_exprs.is_empty());
72            let stmts = thin_vec![call_hash(discr_field.span, discr_field.self_expr.clone())];
73            (stmts, match_expr.clone())
74        }
75        _ => cx.dcx().span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
76    };
77
78    BlockOrExpr::new_mixed(stmts, match_expr)
79}
rustc_builtin_macros/deriving/hash.rs

rustc_builtin_macros/deriving/
hash.rs
