98 lines
3.3 KiB
Rust
98 lines
3.3 KiB
Rust
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use ast::{MetaItem, Item, Expr, MutMutable};
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use codemap::Span;
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use ext::base::ExtCtxt;
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use ext::build::AstBuilder;
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use ext::deriving::generic::*;
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use parse::token::InternedString;
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pub fn expand_deriving_hash(cx: &mut ExtCtxt,
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span: Span,
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mitem: @MetaItem,
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item: @Item,
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push: |@Item|) {
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let allow_default_type_param_usage = cx.attribute(
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span,
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cx.meta_list(
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span,
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InternedString::new("allow"),
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~[cx.meta_word(span, InternedString::new("default_type_param_usage"))]));
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let hash_trait_def = TraitDef {
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span: span,
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attributes: ~[allow_default_type_param_usage],
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path: Path::new_(~["std", "hash", "Hash"], None,
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~[~Literal(Path::new_local("__H"))], true),
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additional_bounds: ~[],
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generics: LifetimeBounds {
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lifetimes: ~[],
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bounds: ~[("__H", ~[Path::new(~["std", "io", "Writer"])])],
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},
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methods: ~[
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MethodDef {
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name: "hash",
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generics: LifetimeBounds::empty(),
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explicit_self: borrowed_explicit_self(),
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args: ~[Ptr(~Literal(Path::new_local("__H")),
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Borrowed(None, MutMutable))],
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ret_ty: nil_ty(),
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inline: true,
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const_nonmatching: false,
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combine_substructure: hash_substructure
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}
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]
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};
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hash_trait_def.expand(cx, mitem, item, push);
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}
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fn hash_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> @Expr {
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let state_expr = match substr.nonself_args {
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[state_expr] => state_expr,
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_ => cx.span_bug(trait_span, "incorrect number of arguments in `deriving(Hash)`")
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};
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let hash_ident = substr.method_ident;
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let call_hash = |span, thing_expr| {
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let expr = cx.expr_method_call(span, thing_expr, hash_ident, ~[state_expr]);
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cx.stmt_expr(expr)
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};
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let mut stmts = ~[];
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let fields = match *substr.fields {
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Struct(ref fs) => fs,
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EnumMatching(index, variant, ref fs) => {
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// Determine the discriminant. We will feed this value to the byte
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// iteration function.
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let discriminant = match variant.node.disr_expr {
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Some(d) => d,
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None => cx.expr_uint(trait_span, index)
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};
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stmts.push(call_hash(trait_span, discriminant));
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fs
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}
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_ => cx.span_bug(trait_span, "impossible substructure in `deriving(Hash)`")
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};
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for &FieldInfo { self_, span, .. } in fields.iter() {
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stmts.push(call_hash(span, self_));
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}
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if stmts.len() == 0 {
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cx.span_bug(trait_span, "#[deriving(Hash)] needs at least one field");
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}
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cx.expr_block(cx.block(trait_span, stmts, None))
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}
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