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]
60 lines
1.1 KiB
Rust
60 lines
1.1 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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// aux-build:custom_derive_plugin.rs
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// ignore-stage1
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#![feature(plugin, custom_derive)]
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#![plugin(custom_derive_plugin)]
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trait TotalSum {
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fn total_sum(&self) -> isize;
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}
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impl TotalSum for isize {
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fn total_sum(&self) -> isize {
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*self
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}
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}
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struct Seven;
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impl TotalSum for Seven {
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fn total_sum(&self) -> isize {
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7
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}
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}
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#[derive(TotalSum)]
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struct Foo {
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seven: Seven,
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bar: Bar,
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baz: isize,
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}
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#[derive(TotalSum)]
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struct Bar {
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quux: isize,
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bleh: isize,
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}
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pub fn main() {
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let v = Foo {
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seven: Seven,
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bar: Bar {
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quux: 9,
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bleh: 3,
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},
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baz: 80,
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};
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assert_eq!(v.total_sum(), 99);
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}
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