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.
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.
11 use ast::{MetaItem, Item, Expr, MutMutable};
13 use ext::base::ExtCtxt;
14 use ext::build::AstBuilder;
15 use ext::deriving::generic::*;
16 use parse::token::InternedString;
18 pub fn expand_deriving_hash(cx: &mut ExtCtxt,
24 let allow_default_type_param_usage = cx.attribute(
28 InternedString::new("allow"),
29 ~[cx.meta_word(span, InternedString::new("default_type_param_usage"))]));
31 let hash_trait_def = TraitDef {
33 attributes: ~[allow_default_type_param_usage],
34 path: Path::new_(~["std", "hash", "Hash"], None,
35 ~[~Literal(Path::new_local("__H"))], true),
36 additional_bounds: ~[],
37 generics: LifetimeBounds {
39 bounds: ~[("__H", ~[Path::new(~["std", "io", "Writer"])])],
44 generics: LifetimeBounds::empty(),
45 explicit_self: borrowed_explicit_self(),
46 args: ~[Ptr(~Literal(Path::new_local("__H")),
47 Borrowed(None, MutMutable))],
50 const_nonmatching: false,
51 combine_substructure: hash_substructure
56 hash_trait_def.expand(cx, mitem, item, push);
59 fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> @Expr {
60 let state_expr = match substr.nonself_args {
61 [state_expr] => state_expr,
62 _ => cx.span_bug(trait_span, "incorrect number of arguments in `deriving(Hash)`")
64 let hash_ident = substr.method_ident;
65 let call_hash = |span, thing_expr| {
66 let expr = cx.expr_method_call(span, thing_expr, hash_ident, ~[state_expr]);
71 let fields = match *substr.fields {
73 EnumMatching(index, variant, ref fs) => {
74 // Determine the discriminant. We will feed this value to the byte
75 // iteration function.
76 let discriminant = match variant.node.disr_expr {
78 None => cx.expr_uint(trait_span, index)
81 stmts.push(call_hash(trait_span, discriminant));
85 _ => cx.span_bug(trait_span, "impossible substructure in `deriving(Hash)`")
88 for &FieldInfo { self_, span, .. } in fields.iter() {
89 stmts.push(call_hash(span, self_));
93 cx.span_bug(trait_span, "#[deriving(Hash)] needs at least one field");
96 cx.expr_block(cx.block(trait_span, stmts, None))