mirror of https://github.com/rust-lang/rust
42 lines
1.0 KiB
Rust
42 lines
1.0 KiB
Rust
//@ run-pass
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// Demonstrate the use of the unguarded escape hatch with a trait bound
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// to assert that destructor will not access any dead data.
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//
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// Compare with ui/span/issue28498-reject-trait-bound.rs
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#![feature(dropck_eyepatch)]
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use std::fmt;
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#[derive(Debug)]
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struct ScribbleOnDrop(String);
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impl Drop for ScribbleOnDrop {
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fn drop(&mut self) {
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self.0 = format!("DROPPED");
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}
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}
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struct Foo<T: fmt::Debug>(u32, T);
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unsafe impl<#[may_dangle] T: fmt::Debug> Drop for Foo<T> {
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fn drop(&mut self) {
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// Use of `may_dangle` is sound, because destructor never accesses
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// the `Debug::fmt` method of `T`, despite having it available.
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println!("Dropping Foo({}, _)", self.0);
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}
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}
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fn main() {
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let (last_dropped, foo0);
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let (foo1, first_dropped);
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last_dropped = ScribbleOnDrop(format!("last"));
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first_dropped = ScribbleOnDrop(format!("first"));
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foo0 = Foo(0, &last_dropped);
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foo1 = Foo(1, &first_dropped);
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println!("foo0.1: {:?} foo1.1: {:?}", foo0.1, foo1.1);
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}
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