c1cda0793e
Some compile-fail tests illustrated cases to be rejected by dropck, including ones that check cyclic data cases designed to exposed bugs if they are actually tricked into running by an unsound analysis. E.g. these exposed bugs in earlier broken ways of handling `Vec<T>`. (Note that all the uses of `unsafe_destructor` are just placating the simple analysis used for that feature, which will eventually go away once we have put the dropck through its paces.)
56 lines
1.7 KiB
Rust
56 lines
1.7 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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// A simple example of an unsound mixing of cyclic structure and Drop.
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//
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// Each `D` has a name and an optional reference to another `D`
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// sibling, but also implements a drop method that prints out its own
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// name as well as the name of its sibling.
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//
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// By setting up a cyclic structure, the drop code cannot possibly
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// work. Therefore this code must be rejected.
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//
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// (As it turns out, essentially any attempt to install a sibling here
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// will be rejected, regardless of whether it forms a cyclic
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// structure or not. This is because the use of the same lifetime
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// `'a` in `&'a D<'a>` cannot be satisfied when `D<'a>` implements
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// `Drop`.)
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#![feature(unsafe_destructor)]
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use std::cell::Cell;
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struct D<'a> {
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name: String,
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p: Cell<Option<&'a D<'a>>>,
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}
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impl<'a> D<'a> {
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fn new(name: String) -> D<'a> { D { name: name, p: Cell::new(None) } }
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}
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#[unsafe_destructor]
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impl<'a> Drop for D<'a> {
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fn drop(&mut self) {
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println!("dropping {} whose sibling is {:?}",
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self.name, self.p.get().map(|d| &d.name));
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}
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}
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fn g() {
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let (d1, d2) = (D::new(format!("d1")), D::new(format!("d2")));
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d1.p.set(Some(&d2)); //~ ERROR `d2` does not live long enough
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d2.p.set(Some(&d1)); //~ ERROR `d1` does not live long enough
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}
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fn main() {
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g();
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}
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