mirror of https://github.com/rust-lang/rust
38 lines
952 B
Rust
38 lines
952 B
Rust
//@ revisions: current next
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//@ ignore-compare-mode-next-solver (explicit revisions)
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//@[next] compile-flags: -Znext-solver
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// We previously wrongly instantiated binders during trait upcasting,
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// allowing the super trait to be more generic than the sub trait.
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// This was unsound.
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#![feature(trait_upcasting)]
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trait Supertrait<'a, 'b> {
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fn cast(&self, x: &'a str) -> &'b str;
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}
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trait Subtrait<'a, 'b>: Supertrait<'a, 'b> {}
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impl<'a> Supertrait<'a, 'a> for () {
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fn cast(&self, x: &'a str) -> &'a str {
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x
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}
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}
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impl<'a> Subtrait<'a, 'a> for () {}
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fn unsound(x: &dyn for<'a> Subtrait<'a, 'a>) -> &dyn for<'a, 'b> Supertrait<'a, 'b> {
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x //~ ERROR mismatched types
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//[current]~^ ERROR mismatched types
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}
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fn transmute<'a, 'b>(x: &'a str) -> &'b str {
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unsound(&()).cast(x)
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}
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fn main() {
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let x;
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{
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let mut temp = String::from("hello there");
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x = transmute(temp.as_str());
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}
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println!("{x}");
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}
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