src/libsyntax_ext/deriving/hash.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use deriving;
  12 use deriving::generic::*;
  13 use deriving::generic::ty::*;
  14
  15 use syntax::ast::{Expr, MetaItem, Mutability};
  16 use syntax::ext::base::{Annotatable, ExtCtxt};
  17 use syntax::ext::build::AstBuilder;
  18 use syntax::ptr::P;
  19 use syntax_pos::Span;
  20
  21 pub fn expand_deriving_hash(cx: &mut ExtCtxt,
  22                             span: Span,
  23                             mitem: &MetaItem,
  24                             item: &Annotatable,
  25                             push: &mut FnMut(Annotatable)) {
  26
  27     let path = Path::new_(pathvec_std!(cx, core::hash::Hash), None, vec![], true);
  28
  29     let typaram = &*deriving::hygienic_type_parameter(item, "__H");
  30
  31     let arg = Path::new_local(typaram);
  32     let hash_trait_def = TraitDef {
  33         span: span,
  34         attributes: Vec::new(),
  35         path: path,
  36         additional_bounds: Vec::new(),
  37         generics: LifetimeBounds::empty(),
  38         is_unsafe: false,
  39         methods: vec![MethodDef {
  40                           name: "hash",
  41                           generics: LifetimeBounds {
  42                               lifetimes: Vec::new(),
  43                               bounds: vec![(typaram, vec![path_std!(cx, core::hash::Hasher)])],
  44                           },
  45                           explicit_self: borrowed_explicit_self(),
  46                           args: vec![Ptr(Box::new(Literal(arg)),
  47                                          Borrowed(None, Mutability::Mutable))],
  48                           ret_ty: nil_ty(),
  49                           attributes: vec![],
  50                           is_unsafe: false,
  51                           unify_fieldless_variants: true,
  52                           combine_substructure: combine_substructure(Box::new(|a, b, c| {
  53                               hash_substructure(a, b, c)
  54                           })),
  55                       }],
  56         associated_types: Vec::new(),
  57     };
  58
  59     hash_trait_def.expand(cx, mitem, item, push);
  60 }
  61
  62 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
  63     let state_expr = match (substr.nonself_args.len(), substr.nonself_args.get(0)) {
  64         (1, Some(o_f)) => o_f,
  65         _ => {
  66             cx.span_bug(trait_span,
  67                         "incorrect number of arguments in `derive(Hash)`")
  68         }
  69     };
  70     let call_hash = |span, thing_expr| {
  71         let hash_path = {
  72             let strs = cx.std_path(&["hash", "Hash", "hash"]);
  73
  74             cx.expr_path(cx.path_global(span, strs))
  75         };
  76         let ref_thing = cx.expr_addr_of(span, thing_expr);
  77         let expr = cx.expr_call(span, hash_path, vec![ref_thing, state_expr.clone()]);
  78         cx.stmt_expr(expr)
  79     };
  80     let mut stmts = Vec::new();
  81
  82     let fields = match *substr.fields {
  83         Struct(_, ref fs) => fs,
  84         EnumMatching(_, _, ref fs) => {
  85             let variant_value = deriving::call_intrinsic(cx,
  86                                                          trait_span,
  87                                                          "discriminant_value",
  88                                                          vec![cx.expr_self(trait_span)]);
  89
  90             stmts.push(call_hash(trait_span, variant_value));
  91
  92             fs
  93         }
  94         _ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
  95     };
  96
  97     for &FieldInfo { ref self_, span, .. } in fields {
  98         stmts.push(call_hash(span, self_.clone()));
  99     }
 100
 101     cx.expr_block(cx.block(trait_span, stmts))
 102 }