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
  17 use std::vec_ng::Vec;
  18
  19 pub fn expand_deriving_hash(cx: &mut ExtCtxt,
  20                             span: Span,
  21                             mitem: @MetaItem,
  22                             item: @Item,
  23                             push: |@Item|) {
  24
  25     let (path, generics, args) = if cx.ecfg.deriving_hash_type_parameter {
  26         (Path::new_(vec!("std", "hash", "Hash"), None,
  27                     vec!(~Literal(Path::new_local("__S"))), true),
  28          LifetimeBounds {
  29              lifetimes: Vec::new(),
  30              bounds: vec!(("__S", vec!(Path::new(vec!("std", "io", "Writer"))))),
  31          },
  32          Path::new_local("__S"))
  33     } else {
  34         (Path::new(vec!("std", "hash", "Hash")),
  35          LifetimeBounds::empty(),
  36          Path::new(vec!("std", "hash", "sip", "SipState")))
  37     };
  38     let hash_trait_def = TraitDef {
  39         span: span,
  40         attributes: Vec::new(),
  41         path: path,
  42         additional_bounds: Vec::new(),
  43         generics: generics,
  44         methods: vec!(
  45             MethodDef {
  46                 name: "hash",
  47                 generics: LifetimeBounds::empty(),
  48                 explicit_self: borrowed_explicit_self(),
  49                 args: vec!(Ptr(~Literal(args), Borrowed(None, MutMutable))),
  50                 ret_ty: nil_ty(),
  51                 inline: true,
  52                 const_nonmatching: false,
  53                 combine_substructure: hash_substructure
  54             }
  55         )
  56     };
  57
  58     hash_trait_def.expand(cx, mitem, item, push);
  59 }
  60
  61 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> @Expr {
  62     let state_expr = match substr.nonself_args {
  63         [state_expr] => state_expr,
  64         _ => cx.span_bug(trait_span, "incorrect number of arguments in `deriving(Hash)`")
  65     };
  66     let hash_ident = substr.method_ident;
  67     let call_hash = |span, thing_expr| {
  68         let expr = cx.expr_method_call(span, thing_expr, hash_ident, vec!(state_expr));
  69         cx.stmt_expr(expr)
  70     };
  71     let mut stmts = Vec::new();
  72
  73     let fields = match *substr.fields {
  74         Struct(ref fs) => fs,
  75         EnumMatching(index, variant, ref fs) => {
  76             // Determine the discriminant. We will feed this value to the byte
  77             // iteration function.
  78             let discriminant = match variant.node.disr_expr {
  79                 Some(d) => d,
  80                 None => cx.expr_uint(trait_span, index)
  81             };
  82
  83             stmts.push(call_hash(trait_span, discriminant));
  84
  85             fs
  86         }
  87         _ => cx.span_bug(trait_span, "impossible substructure in `deriving(Hash)`")
  88     };
  89
  90     for &FieldInfo { self_, span, .. } in fields.iter() {
  91         stmts.push(call_hash(span, self_));
  92     }
  93
  94     if stmts.len() == 0 {
  95         cx.span_bug(trait_span, "#[deriving(Hash)] needs at least one field");
  96     }
  97
  98     cx.expr_block(cx.block(trait_span, stmts, None))
  99 }