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 parse::token::InternedString;
  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", ast::StaticSize, 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 inline = cx.meta_word(span, InternedString::new("inline"));
  39     let attrs = vec!(cx.attribute(span, inline));
  40     let hash_trait_def = TraitDef {
  41         span: span,
  42         attributes: Vec::new(),
  43         path: path,
  44         additional_bounds: Vec::new(),
  45         generics: generics,
  46         methods: vec!(
  47             MethodDef {
  48                 name: "hash",
  49                 generics: LifetimeBounds::empty(),
  50                 explicit_self: borrowed_explicit_self(),
  51                 args: vec!(Ptr(~Literal(args), Borrowed(None, MutMutable))),
  52                 ret_ty: nil_ty(),
  53                 attributes: attrs,
  54                 const_nonmatching: false,
  55                 combine_substructure: combine_substructure(|a, b, c| {
  56                     hash_substructure(a, b, c)
  57                 })
  58             }
  59         )
  60     };
  61
  62     hash_trait_def.expand(cx, mitem, item, push);
  63 }
  64
  65 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> @Expr {
  66     let state_expr = match substr.nonself_args {
  67         [state_expr] => state_expr,
  68         _ => cx.span_bug(trait_span, "incorrect number of arguments in `deriving(Hash)`")
  69     };
  70     let hash_ident = substr.method_ident;
  71     let call_hash = |span, thing_expr| {
  72         let expr = cx.expr_method_call(span, thing_expr, hash_ident, vec!(state_expr));
  73         cx.stmt_expr(expr)
  74     };
  75     let mut stmts = Vec::new();
  76
  77     let fields = match *substr.fields {
  78         Struct(ref fs) => fs,
  79         EnumMatching(index, variant, ref fs) => {
  80             // Determine the discriminant. We will feed this value to the byte
  81             // iteration function.
  82             let discriminant = match variant.node.disr_expr {
  83                 Some(d) => d,
  84                 None => cx.expr_uint(trait_span, index)
  85             };
  86
  87             stmts.push(call_hash(trait_span, discriminant));
  88
  89             fs
  90         }
  91         _ => cx.span_bug(trait_span, "impossible substructure in `deriving(Hash)`")
  92     };
  93
  94     for &FieldInfo { self_, span, .. } in fields.iter() {
  95         stmts.push(call_hash(span, self_));
  96     }
  97
  98     if stmts.len() == 0 {
  99         cx.span_bug(trait_span, "#[deriving(Hash)] needs at least one field");
 100     }
 101
 102     cx.expr_block(cx.block(trait_span, stmts, None))
 103 }