compiler/rustc_builtin_macros/src/deriving/hash.rs

   1 use crate::deriving::generic::ty::*;
   2 use crate::deriving::generic::*;
   3 use crate::deriving::{self, path_std, pathvec_std};
   4
   5 use rustc_ast::ptr::P;
   6 use rustc_ast::{Expr, MetaItem, Mutability};
   7 use rustc_expand::base::{Annotatable, ExtCtxt};
   8 use rustc_span::symbol::sym;
   9 use rustc_span::Span;
  10
  11 pub fn expand_deriving_hash(
  12     cx: &mut ExtCtxt<'_>,
  13     span: Span,
  14     mitem: &MetaItem,
  15     item: &Annotatable,
  16     push: &mut dyn FnMut(Annotatable),
  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         attributes: Vec::new(),
  26         path,
  27         additional_bounds: Vec::new(),
  28         generics: Bounds::empty(),
  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             args: vec![(Ref(Box::new(Literal(arg)), Mutability::Mut), sym::state)],
  35             ret_ty: nil_ty(),
  36             attributes: vec![],
  37             unify_fieldless_variants: true,
  38             combine_substructure: combine_substructure(Box::new(|a, b, c| {
  39                 hash_substructure(a, b, c)
  40             })),
  41         }],
  42         associated_types: Vec::new(),
  43     };
  44
  45     hash_trait_def.expand(cx, mitem, item, push);
  46 }
  47
  48 fn hash_substructure(cx: &mut ExtCtxt<'_>, trait_span: Span, substr: &Substructure<'_>) -> P<Expr> {
  49     let [state_expr] = substr.nonself_args else {
  50         cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`");
  51     };
  52     let call_hash = |span, thing_expr| {
  53         let hash_path = {
  54             let strs = cx.std_path(&[sym::hash, sym::Hash, sym::hash]);
  55
  56             cx.expr_path(cx.path_global(span, strs))
  57         };
  58         let ref_thing = cx.expr_addr_of(span, thing_expr);
  59         let expr = cx.expr_call(span, hash_path, vec![ref_thing, state_expr.clone()]);
  60         cx.stmt_expr(expr)
  61     };
  62     let mut stmts = Vec::new();
  63
  64     let fields = match substr.fields {
  65         Struct(_, fs) | EnumMatching(_, 1, .., fs) => fs,
  66         EnumMatching(.., fs) => {
  67             let variant_value = deriving::call_intrinsic(
  68                 cx,
  69                 trait_span,
  70                 sym::discriminant_value,
  71                 vec![cx.expr_self(trait_span)],
  72             );
  73
  74             stmts.push(call_hash(trait_span, variant_value));
  75
  76             fs
  77         }
  78         _ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
  79     };
  80
  81     stmts.extend(
  82         fields.iter().map(|FieldInfo { ref self_, span, .. }| call_hash(*span, self_.clone())),
  83     );
  84
  85     cx.expr_block(cx.block(trait_span, stmts))
  86 }