9249e6a1e2
Changes #[derive(Copy, Clone)] to use a faster impl of Clone when both derives are present, and there are no generics in the type. The faster impl is simply returning *self (which works because the type is also Copy). See the comments in libsyntax_ext/deriving/clone.rs for more details. There are a few types which are Copy but not Clone, in violation of the definition of Copy. These include large arrays and tuples. The very existence of these types is arguably a bug, but in order for this optimization not to change the applicability of #[derive(Copy, Clone)], the faster Clone impl also injects calls to a new function, core::clone::assert_receiver_is_clone, to verify that all members are actually Clone. This is not a breaking change, because pursuant to RFC 1521, any type that implements Copy should not do any observable work in its Clone impl.
33 lines
1 KiB
Rust
33 lines
1 KiB
Rust
// Copyright 2012 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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#![allow(unknown_features)]
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#![feature(box_syntax)]
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#[derive(Copy, Clone)]
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enum side { mayo, catsup, vinegar }
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#[derive(Copy, Clone)]
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enum order { hamburger, fries(side), shake }
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#[derive(Copy, Clone)]
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enum meal { to_go(order), for_here(order) }
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fn foo(m: Box<meal>, cond: bool) {
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match *m {
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meal::to_go(_) => { }
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meal::for_here(_) if cond => {}
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meal::for_here(order::hamburger) => {}
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meal::for_here(order::fries(_s)) => {}
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meal::for_here(order::shake) => {}
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}
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}
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pub fn main() {
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foo(box meal::for_here(order::hamburger), true)
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}
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