491054f08e
This is a hack, but I don't think we can do much better as long as `derive` is
running at the syntax expansion phase.
If the custom_derive feature gate is enabled, this works with user-defined
traits and syntax extensions. Without the gate, you can't use e.g. #[derive_Clone]
directly, so this does not change the stable language.
This commit also cleans up the deriving code somewhat, and forbids some
previously-meaningless attribute syntax. For this reason it's technically a
[breaking-change]
75 lines
2.6 KiB
Rust
75 lines
2.6 KiB
Rust
// Copyright 2015 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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// force-host
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#![feature(plugin_registrar)]
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#![feature(box_syntax)]
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#![feature(rustc_private)]
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extern crate syntax;
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extern crate rustc;
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use syntax::ast;
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use syntax::codemap::Span;
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use syntax::ext::base::{Decorator, ExtCtxt};
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use syntax::ext::build::AstBuilder;
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use syntax::ext::deriving::generic::{cs_fold, TraitDef, MethodDef, combine_substructure};
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use syntax::ext::deriving::generic::ty::{Literal, LifetimeBounds, Path, borrowed_explicit_self};
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use syntax::parse::token;
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use syntax::ptr::P;
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use rustc::plugin::Registry;
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#[plugin_registrar]
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pub fn plugin_registrar(reg: &mut Registry) {
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reg.register_syntax_extension(
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token::intern("derive_TotalSum"),
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Decorator(box expand));
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}
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fn expand(cx: &mut ExtCtxt,
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span: Span,
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mitem: &ast::MetaItem,
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item: &ast::Item,
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push: &mut FnMut(P<ast::Item>)) {
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let trait_def = TraitDef {
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span: span,
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attributes: vec![],
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path: Path::new(vec!["TotalSum"]),
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additional_bounds: vec![],
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generics: LifetimeBounds::empty(),
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associated_types: vec![],
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methods: vec![
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MethodDef {
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name: "total_sum",
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generics: LifetimeBounds::empty(),
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explicit_self: borrowed_explicit_self(),
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args: vec![],
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ret_ty: Literal(Path::new_local("isize")),
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attributes: vec![],
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combine_substructure: combine_substructure(box |cx, span, substr| {
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let zero = cx.expr_int(span, 0);
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cs_fold(false,
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|cx, span, subexpr, field, _| {
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cx.expr_binary(span, ast::BiAdd, subexpr,
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cx.expr_method_call(span, field,
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token::str_to_ident("total_sum"), vec![]))
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},
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zero,
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box |cx, span, _, _| { cx.span_bug(span, "wtf??"); },
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cx, span, substr)
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}),
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},
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],
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};
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trait_def.expand(cx, mitem, item, |i| push(i))
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}
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