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, Item, Expr, MutMutable};
  12 use codemap::Span;
  13 use ext::base::ExtCtxt;
  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<F>(cx: &mut ExtCtxt,
  20                                span: Span,
  21                                mitem: &MetaItem,
  22                                item: &Item,
  23                                push: F) where
  24     F: FnOnce(P<Item>),
  25 {
  26
  27     let path = Path::new_(pathvec_std!(cx, core::hash::Hash), None,
  28                           vec!(), true);
  29     let arg = Path::new_local("__H");
  30     let hash_trait_def = TraitDef {
  31         span: span,
  32         attributes: Vec::new(),
  33         path: path,
  34         additional_bounds: Vec::new(),
  35         generics: LifetimeBounds::empty(),
  36         methods: vec!(
  37             MethodDef {
  38                 name: "hash",
  39                 generics: LifetimeBounds {
  40                     lifetimes: Vec::new(),
  41                     bounds: vec![("__H",
  42                                   vec![path_std!(cx, core::hash::Hasher)])],
  43                 },
  44                 explicit_self: borrowed_explicit_self(),
  45                 args: vec!(Ptr(box Literal(arg), Borrowed(None, MutMutable))),
  46                 ret_ty: nil_ty(),
  47                 attributes: vec![],
  48                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
  49                     hash_substructure(a, b, c)
  50                 }))
  51             }
  52         ),
  53         associated_types: Vec::new(),
  54     };
  55
  56     hash_trait_def.expand(cx, mitem, item, push);
  57 }
  58
  59 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
  60     let state_expr = match substr.nonself_args {
  61         [ref state_expr] => state_expr,
  62         _ => cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`")
  63     };
  64     let call_hash = |span, thing_expr| {
  65         let hash_path = {
  66             let strs = vec![
  67                 cx.ident_of_std("core"),
  68                 cx.ident_of("hash"),
  69                 cx.ident_of("Hash"),
  70                 cx.ident_of("hash"),
  71             ];
  72
  73             cx.expr_path(cx.path_global(span, strs))
  74         };
  75         let ref_thing = cx.expr_addr_of(span, thing_expr);
  76         let expr = cx.expr_call(span, hash_path, vec!(ref_thing, state_expr.clone()));
  77         cx.stmt_expr(expr)
  78     };
  79     let mut stmts = Vec::new();
  80
  81     let fields = match *substr.fields {
  82         Struct(ref fs) => fs,
  83         EnumMatching(index, variant, ref fs) => {
  84             // Determine the discriminant. We will feed this value to the byte
  85             // iteration function.
  86             let discriminant = match variant.node.disr_expr {
  87                 Some(ref d) => d.clone(),
  88                 None => cx.expr_usize(trait_span, index)
  89             };
  90
  91             stmts.push(call_hash(trait_span, discriminant));
  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, None))
 103 }