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         skip_path_as_bound: false,
  26         additional_bounds: Vec::new(),
  27         generics: Bounds::empty(),
  28         supports_unions: false,
  29         methods: vec![MethodDef {
  30             name: sym::hash,
  31             generics: Bounds { bounds: vec![(typaram, vec![path_std!(hash::Hasher)])] },
  32             explicit_self: true,
  33             nonself_args: vec![(Ref(Box::new(Path(arg)), Mutability::Mut), sym::state)],
  34             ret_ty: Unit,
  35             attributes: AttrVec::new(),
  36             unify_fieldless_variants: true,
  37             combine_substructure: combine_substructure(Box::new(|a, b, c| {
  38                 hash_substructure(a, b, c)
  39             })),
  40         }],
  41         associated_types: Vec::new(),
  42     };
  43
  44     hash_trait_def.expand(cx, mitem, item, push);
  45 }
  46
  47 fn hash_substructure(
  48     cx: &mut ExtCtxt<'_>,
  49     trait_span: Span,
  50     substr: &Substructure<'_>,
  51 ) -> BlockOrExpr {
  52     let [state_expr] = substr.nonselflike_args else {
  53         cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`");
  54     };
  55     let call_hash = |span, expr| {
  56         let hash_path = {
  57             let strs = cx.std_path(&[sym::hash, sym::Hash, sym::hash]);
  58
  59             cx.expr_path(cx.path_global(span, strs))
  60         };
  61         let expr = cx.expr_call(span, hash_path, vec![expr, state_expr.clone()]);
  62         cx.stmt_expr(expr)
  63     };
  64
  65     let (stmts, match_expr) = match substr.fields {
  66         Struct(_, fields) | EnumMatching(.., fields) => {
  67             let stmts =
  68                 fields.iter().map(|field| call_hash(field.span, field.self_expr.clone())).collect();
  69             (stmts, None)
  70         }
  71         EnumTag(tag_field, match_expr) => {
  72             assert!(tag_field.other_selflike_exprs.is_empty());
  73             let stmts = vec![call_hash(tag_field.span, tag_field.self_expr.clone())];
  74             (stmts, match_expr.clone())
  75         }
  76         _ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
  77     };
  78
  79     BlockOrExpr::new_mixed(stmts, match_expr)
  80 }