49 lines
1.5 KiB
Rust
49 lines
1.5 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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// A dummy trait/impl that work close over any type. The trait will
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// be parameterized by a region due to the &self/int constraint.
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trait foo {
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fn foo(i: &self/int) -> int;
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}
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impl<T:Copy> foo for T {
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fn foo(i: &self/int) -> int {*i}
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}
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fn to_foo<T:Copy>(t: T) {
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// This version is ok because, although T may contain borrowed
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// pointers, it never escapes the fn body. We know this because
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// the type of foo includes a region which will be resolved to
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// the fn body itself.
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let v = &3;
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struct F<T> { f: T }
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let x = F {f:t} as foo;
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assert x.foo(v) == 3;
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}
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fn to_foo_2<T:Copy>(t: T) -> foo {
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// Not OK---T may contain borrowed ptrs and it is going to escape
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// as part of the returned foo value
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struct F<T> { f: T }
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F {f:t} as foo //~ ERROR value may contain borrowed pointers; use `&static` bound
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}
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fn to_foo_3<T:Copy + &static>(t: T) -> foo {
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// OK---T may escape as part of the returned foo value, but it is
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// owned and hence does not contain borrowed ptrs
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struct F<T> { f: T }
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F {f:t} as foo
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}
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fn main() {
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}
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