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!(box 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(box 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 }