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;
  12 use ast::{MetaItem, Item, Expr, MutMutable};
  13 use codemap::Span;
  14 use ext::base::ExtCtxt;
  15 use ext::build::AstBuilder;
  16 use ext::deriving::generic::*;
  17 use ext::deriving::generic::ty::*;
  18 use parse::token::InternedString;
  19
  20 use std::gc::Gc;
  21
  22 pub fn expand_deriving_hash(cx: &mut ExtCtxt,
  23                             span: Span,
  24                             mitem: Gc<MetaItem>,
  25                             item: Gc<Item>,
  26                             push: |Gc<Item>|) {
  27
  28     let (path, generics, args) = if cx.ecfg.deriving_hash_type_parameter {
  29         (Path::new_(vec!("std", "hash", "Hash"), None,
  30                     vec!(box Literal(Path::new_local("__S"))), true),
  31          LifetimeBounds {
  32              lifetimes: Vec::new(),
  33              bounds: vec!(("__S", ast::StaticSize,
  34                            vec!(Path::new(vec!("std", "hash", "Writer"))))),
  35          },
  36          Path::new_local("__S"))
  37     } else {
  38         (Path::new(vec!("std", "hash", "Hash")),
  39          LifetimeBounds::empty(),
  40          Path::new(vec!("std", "hash", "sip", "SipState")))
  41     };
  42     let inline = cx.meta_word(span, InternedString::new("inline"));
  43     let attrs = vec!(cx.attribute(span, inline));
  44     let hash_trait_def = TraitDef {
  45         span: span,
  46         attributes: Vec::new(),
  47         path: path,
  48         additional_bounds: Vec::new(),
  49         generics: generics,
  50         methods: vec!(
  51             MethodDef {
  52                 name: "hash",
  53                 generics: LifetimeBounds::empty(),
  54                 explicit_self: borrowed_explicit_self(),
  55                 args: vec!(Ptr(box Literal(args), Borrowed(None, MutMutable))),
  56                 ret_ty: nil_ty(),
  57                 attributes: attrs,
  58                 const_nonmatching: false,
  59                 combine_substructure: combine_substructure(|a, b, c| {
  60                     hash_substructure(a, b, c)
  61                 })
  62             }
  63         )
  64     };
  65
  66     hash_trait_def.expand(cx, mitem, item, push);
  67 }
  68
  69 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span,
  70                      substr: &Substructure) -> Gc<Expr> {
  71     let state_expr = match substr.nonself_args {
  72         [state_expr] => state_expr,
  73         _ => cx.span_bug(trait_span, "incorrect number of arguments in `deriving(Hash)`")
  74     };
  75     let hash_ident = substr.method_ident;
  76     let call_hash = |span, thing_expr| {
  77         let expr = cx.expr_method_call(span, thing_expr, hash_ident, vec!(state_expr));
  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(index, variant, ref fs) => {
  85             // Determine the discriminant. We will feed this value to the byte
  86             // iteration function.
  87             let discriminant = match variant.node.disr_expr {
  88                 Some(d) => d,
  89                 None => cx.expr_uint(trait_span, index)
  90             };
  91
  92             stmts.push(call_hash(trait_span, discriminant));
  93
  94             fs
  95         }
  96         _ => cx.span_bug(trait_span, "impossible substructure in `deriving(Hash)`")
  97     };
  98
  99     for &FieldInfo { self_, span, .. } in fields.iter() {
 100         stmts.push(call_hash(span, self_));
 101     }
 102
 103     if stmts.len() == 0 {
 104         cx.span_bug(trait_span, "#[deriving(Hash)] needs at least one field");
 105     }
 106
 107     cx.expr_block(cx.block(trait_span, stmts, None))
 108 }