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 ) {
  17     let path = Path::new_(pathvec_std!(hash::Hash), vec![], PathKind::Std);
  18
  19     let typaram = sym::__H;
  20
  21     let arg = Path::new_local(typaram);
  22     let hash_trait_def = TraitDef {
  23         span,
  24         path,
  25         additional_bounds: Vec::new(),
  26         generics: Bounds::empty(),
  27         supports_unions: false,
  28         methods: vec![MethodDef {
  29             name: sym::hash,
  30             generics: Bounds { bounds: vec![(typaram, vec![path_std!(hash::Hasher)])] },
  31             explicit_self: true,
  32             nonself_args: vec![(Ref(Box::new(Path(arg)), Mutability::Mut), sym::state)],
  33             ret_ty: Unit,
  34             attributes: AttrVec::new(),
  35             unify_fieldless_variants: true,
  36             combine_substructure: combine_substructure(Box::new(|a, b, c| {
  37                 hash_substructure(a, b, c)
  38             })),
  39         }],
  40         associated_types: Vec::new(),
  41     };
  42
  43     hash_trait_def.expand(cx, mitem, item, push);
  44 }
  45
  46 fn hash_substructure(
  47     cx: &mut ExtCtxt<'_>,
  48     trait_span: Span,
  49     substr: &Substructure<'_>,
  50 ) -> BlockOrExpr {
  51     let [state_expr] = substr.nonselflike_args else {
  52         cx.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, 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         EnumTag(tag_field, match_expr) => {
  71             assert!(tag_field.other_selflike_exprs.is_empty());
  72             let stmts = vec![call_hash(tag_field.span, tag_field.self_expr.clone())];
  73             (stmts, match_expr.clone())
  74         }
  75         _ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
  76     };
  77
  78     BlockOrExpr::new_mixed(stmts, match_expr)
  79 }