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