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 ast::{MetaItem, Expr, MutMutable};
  12 use codemap::Span;
  13 use ext::base::{ExtCtxt, Annotatable};
  14 use ext::build::AstBuilder;
  15 use ext::deriving::generic::*;
  16 use ext::deriving::generic::ty::*;
  17 use ptr::P;
  18
  19 pub fn expand_deriving_hash(cx: &mut ExtCtxt,
  20                             span: Span,
  21                             mitem: &MetaItem,
  22                             item: Annotatable,
  23                             push: &mut FnMut(Annotatable))
  24 {
  25
  26     let path = Path::new_(pathvec_std!(cx, core::hash::Hash), None,
  27                           vec!(), true);
  28     let arg = Path::new_local("__H");
  29     let hash_trait_def = TraitDef {
  30         span: span,
  31         attributes: Vec::new(),
  32         path: path,
  33         additional_bounds: Vec::new(),
  34         generics: LifetimeBounds::empty(),
  35         methods: vec!(
  36             MethodDef {
  37                 name: "hash",
  38                 generics: LifetimeBounds {
  39                     lifetimes: Vec::new(),
  40                     bounds: vec![("__H",
  41                                   vec![path_std!(cx, core::hash::Hasher)])],
  42                 },
  43                 explicit_self: borrowed_explicit_self(),
  44                 args: vec!(Ptr(Box::new(Literal(arg)), Borrowed(None, MutMutable))),
  45                 ret_ty: nil_ty(),
  46                 attributes: vec![],
  47                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
  48                     hash_substructure(a, b, c)
  49                 }))
  50             }
  51         ),
  52         associated_types: Vec::new(),
  53     };
  54
  55     hash_trait_def.expand(cx, mitem, &item, push);
  56 }
  57
  58 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
  59     let state_expr = match (substr.nonself_args.len(), substr.nonself_args.get(0)) {
  60         (1, Some(o_f)) => o_f,
  61         _ => cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`")
  62     };
  63     let call_hash = |span, thing_expr| {
  64         let hash_path = {
  65             let strs = vec![
  66                 cx.ident_of_std("core"),
  67                 cx.ident_of("hash"),
  68                 cx.ident_of("Hash"),
  69                 cx.ident_of("hash"),
  70             ];
  71
  72             cx.expr_path(cx.path_global(span, strs))
  73         };
  74         let ref_thing = cx.expr_addr_of(span, thing_expr);
  75         let expr = cx.expr_call(span, hash_path, vec!(ref_thing, state_expr.clone()));
  76         cx.stmt_expr(expr)
  77     };
  78     let mut stmts = Vec::new();
  79
  80     let fields = match *substr.fields {
  81         Struct(ref fs) => fs,
  82         EnumMatching(index, variant, ref fs) => {
  83             // Determine the discriminant. We will feed this value to the byte
  84             // iteration function.
  85             let discriminant = match variant.node.disr_expr {
  86                 Some(ref d) => d.clone(),
  87                 None => cx.expr_usize(trait_span, index)
  88             };
  89
  90             stmts.push(call_hash(trait_span, discriminant));
  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, None))
 102 }