compiler/rustc_builtin_macros/src/deriving/hash.rs

   1 use crate::deriving::generic::ty::*;
   2 use crate::deriving::generic::*;
   3 use crate::deriving::{path_std, pathvec_std};
   4
   5 use rustc_ast::{AttrVec, MetaItem, Mutability};
   6 use rustc_expand::base::{Annotatable, ExtCtxt};
   7 use rustc_span::symbol::sym;
   8 use rustc_span::Span;
   9
  10 pub fn expand_deriving_hash(
  11     cx: &mut 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: AttrVec::new(),
  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     };
  45
  46     hash_trait_def.expand(cx, mitem, item, push);
  47 }
  48
  49 fn hash_substructure(
  50     cx: &mut ExtCtxt<'_>,
  51     trait_span: Span,
  52     substr: &Substructure<'_>,
  53 ) -> BlockOrExpr {
  54     let [state_expr] = substr.nonselflike_args else {
  55         cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`");
  56     };
  57     let call_hash = |span, expr| {
  58         let hash_path = {
  59             let strs = cx.std_path(&[sym::hash, sym::Hash, sym::hash]);
  60
  61             cx.expr_path(cx.path_global(span, strs))
  62         };
  63         let expr = cx.expr_call(span, hash_path, vec![expr, state_expr.clone()]);
  64         cx.stmt_expr(expr)
  65     };
  66
  67     let (stmts, match_expr) = match substr.fields {
  68         Struct(_, fields) | EnumMatching(.., fields) => {
  69             let stmts =
  70                 fields.iter().map(|field| call_hash(field.span, field.self_expr.clone())).collect();
  71             (stmts, None)
  72         }
  73         EnumTag(tag_field, match_expr) => {
  74             assert!(tag_field.other_selflike_exprs.is_empty());
  75             let stmts = vec![call_hash(tag_field.span, tag_field.self_expr.clone())];
  76             (stmts, match_expr.clone())
  77         }
  78         _ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
  79     };
  80
  81     BlockOrExpr::new_mixed(stmts, match_expr)
  82 }