mirror of https://github.com/rust-lang/rust.git
46 lines
1.2 KiB
Rust
46 lines
1.2 KiB
Rust
// Test to ensure that trait bounds are properly
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// checked on specializable associated types
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#![allow(incomplete_features)]
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#![feature(specialization)]
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trait UncheckedCopy: Sized {
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type Output: From<Self> + Copy + Into<Self>;
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}
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impl<T> UncheckedCopy for T {
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default type Output = Self;
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//~^ ERROR: the trait bound `T: Copy` is not satisfied
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}
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fn unchecked_copy<T: UncheckedCopy>(other: &T::Output) -> T {
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(*other).into()
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}
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fn bug(origin: String) {
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// Turn the String into it's Output type...
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// Which we can just do by `.into()`, the assoc type states `From<Self>`.
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let origin_output = origin.into();
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// Make a copy of String::Output, which is a String...
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let mut copy: String = unchecked_copy::<String>(&origin_output);
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// Turn the Output type into a String again,
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// Which we can just do by `.into()`, the assoc type states `Into<Self>`.
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let mut origin: String = origin_output.into();
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// assert both Strings use the same buffer.
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assert_eq!(copy.as_ptr(), origin.as_ptr());
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// Any use of the copy we made becomes invalid,
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drop(origin);
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// OH NO! UB UB UB UB!
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copy.push_str(" world!");
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println!("{}", copy);
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}
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fn main() {
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bug(String::from("hello"));
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}
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