47 lines
1.1 KiB
Rust
47 lines
1.1 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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// Check that a trait is still object-safe (and usable) if it has
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// generic methods so long as they require `Self : Sized`.
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trait Counter {
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fn tick(&mut self) -> u32;
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fn with<F:FnOnce(u32)>(&self, f: F) where Self : Sized;
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}
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struct CCounter {
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c: u32
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}
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impl Counter for CCounter {
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fn tick(&mut self) -> u32 { self.c += 1; self.c }
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fn with<F:FnOnce(u32)>(&self, f: F) { f(self.c); }
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}
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fn tick1<C:Counter>(c: &mut C) {
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tick2(c);
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c.with(|i| ());
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}
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fn tick2(c: &mut Counter) {
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tick3(c);
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}
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fn tick3<C:?Sized+Counter>(c: &mut C) {
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c.tick();
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c.tick();
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}
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fn main() {
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let mut c = CCounter { c: 0 };
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tick1(&mut c);
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assert_eq!(c.tick(), 3);
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}
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