src/librustc_builtin_macros/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::ast::{Expr, MetaItem, Mutability};
   6 use rustc_ast::ptr::P;
   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!(cx, hash::Hash), None, vec![], PathKind::Std);
  19
  20     let typaram = "__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: LifetimeBounds::empty(),
  29         is_unsafe: false,
  30         supports_unions: false,
  31         methods: vec![MethodDef {
  32             name: "hash",
  33             generics: LifetimeBounds {
  34                 lifetimes: Vec::new(),
  35                 bounds: vec![(typaram, vec![path_std!(cx, hash::Hasher)])],
  36             },
  37             explicit_self: borrowed_explicit_self(),
  38             args: vec![(Ptr(Box::new(Literal(arg)), Borrowed(None, Mutability::Mut)), "state")],
  39             ret_ty: nil_ty(),
  40             attributes: vec![],
  41             is_unsafe: false,
  42             unify_fieldless_variants: true,
  43             combine_substructure: combine_substructure(Box::new(|a, b, c| {
  44                 hash_substructure(a, b, c)
  45             })),
  46         }],
  47         associated_types: Vec::new(),
  48     };
  49
  50     hash_trait_def.expand(cx, mitem, item, push);
  51 }
  52
  53 fn hash_substructure(cx: &mut ExtCtxt<'_>, trait_span: Span, substr: &Substructure<'_>) -> P<Expr> {
  54     let state_expr = match &substr.nonself_args {
  55         &[o_f] => o_f,
  56         _ => cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`"),
  57     };
  58     let call_hash = |span, thing_expr| {
  59         let hash_path = {
  60             let strs = cx.std_path(&[sym::hash, sym::Hash, sym::hash]);
  61
  62             cx.expr_path(cx.path_global(span, strs))
  63         };
  64         let ref_thing = cx.expr_addr_of(span, thing_expr);
  65         let expr = cx.expr_call(span, hash_path, vec![ref_thing, state_expr.clone()]);
  66         cx.stmt_expr(expr)
  67     };
  68     let mut stmts = Vec::new();
  69
  70     let fields = match *substr.fields {
  71         Struct(_, ref fs) | EnumMatching(_, 1, .., ref fs) => fs,
  72         EnumMatching(.., ref fs) => {
  73             let variant_value = deriving::call_intrinsic(
  74                 cx,
  75                 trait_span,
  76                 "discriminant_value",
  77                 vec![cx.expr_self(trait_span)],
  78             );
  79
  80             stmts.push(call_hash(trait_span, variant_value));
  81
  82             fs
  83         }
  84         _ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
  85     };
  86
  87     stmts.extend(
  88         fields.iter().map(|FieldInfo { ref self_, span, .. }| call_hash(*span, self_.clone())),
  89     );
  90
  91     cx.expr_block(cx.block(trait_span, stmts))
  92 }