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::{MetaItem, Expr, Mutability};
  16 use syntax::ext::base::{ExtCtxt, Annotatable};
  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
  28     let path = Path::new_(pathvec_std!(cx, core::hash::Hash), None,
  29                           vec!(), true);
  30
  31     let typaram = &*deriving::hygienic_type_parameter(item, "__H");
  32
  33     let arg = Path::new_local(typaram);
  34     let hash_trait_def = TraitDef {
  35         span: span,
  36         attributes: Vec::new(),
  37         path: path,
  38         additional_bounds: Vec::new(),
  39         generics: LifetimeBounds::empty(),
  40         is_unsafe: false,
  41         methods: vec!(
  42             MethodDef {
  43                 name: "hash",
  44                 generics: LifetimeBounds {
  45                     lifetimes: Vec::new(),
  46                     bounds: vec![(typaram,
  47                                   vec![path_std!(cx, core::hash::Hasher)])],
  48                 },
  49                 explicit_self: borrowed_explicit_self(),
  50                 args: vec!(Ptr(Box::new(Literal(arg)), Borrowed(None, Mutability::Mutable))),
  51                 ret_ty: nil_ty(),
  52                 attributes: vec![],
  53                 is_unsafe: false,
  54                 unify_fieldless_variants: true,
  55                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
  56                     hash_substructure(a, b, c)
  57                 }))
  58             }
  59         ),
  60         associated_types: Vec::new(),
  61     };
  62
  63     hash_trait_def.expand(cx, mitem, item, push);
  64 }
  65
  66 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
  67     let state_expr = match (substr.nonself_args.len(), substr.nonself_args.get(0)) {
  68         (1, Some(o_f)) => o_f,
  69         _ => cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`")
  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 }