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         supports_unions: false,
  40         methods: vec![MethodDef {
  41                           name: "hash",
  42                           generics: LifetimeBounds {
  43                               lifetimes: Vec::new(),
  44                               bounds: vec![(typaram, vec![path_std!(cx, core::hash::Hasher)])],
  45                           },
  46                           explicit_self: borrowed_explicit_self(),
  47                           args: vec![Ptr(Box::new(Literal(arg)),
  48                                          Borrowed(None, Mutability::Mutable))],
  49                           ret_ty: nil_ty(),
  50                           attributes: vec![],
  51                           is_unsafe: false,
  52                           unify_fieldless_variants: true,
  53                           combine_substructure: combine_substructure(Box::new(|a, b, c| {
  54                               hash_substructure(a, b, c)
  55                           })),
  56                       }],
  57         associated_types: Vec::new(),
  58     };
  59
  60     hash_trait_def.expand(cx, mitem, item, push);
  61 }
  62
  63 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
  64     let state_expr = match (substr.nonself_args.len(), substr.nonself_args.get(0)) {
  65         (1, Some(o_f)) => o_f,
  66         _ => {
  67             cx.span_bug(trait_span,
  68                         "incorrect number of arguments in `derive(Hash)`")
  69         }
  70     };
  71     let call_hash = |span, thing_expr| {
  72         let hash_path = {
  73             let strs = cx.std_path(&["hash", "Hash", "hash"]);
  74
  75             cx.expr_path(cx.path_global(span, strs))
  76         };
  77         let ref_thing = cx.expr_addr_of(span, thing_expr);
  78         let expr = cx.expr_call(span, hash_path, vec![ref_thing, state_expr.clone()]);
  79         cx.stmt_expr(expr)
  80     };
  81     let mut stmts = Vec::new();
  82
  83     let fields = match *substr.fields {
  84         Struct(_, ref fs) => fs,
  85         EnumMatching(_, _, ref fs) => {
  86             let variant_value = deriving::call_intrinsic(cx,
  87                                                          trait_span,
  88                                                          "discriminant_value",
  89                                                          vec![cx.expr_self(trait_span)]);
  90
  91             stmts.push(call_hash(trait_span, variant_value));
  92
  93             fs
  94         }
  95         _ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
  96     };
  97
  98     for &FieldInfo { ref self_, span, .. } in fields {
  99         stmts.push(call_hash(span, self_.clone()));
 100     }
 101
 102     cx.expr_block(cx.block(trait_span, stmts))
 103 }