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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:13 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:13 +0000 |
commit | 218caa410aa38c29984be31a5229b9fa717560ee (patch) | |
tree | c54bd55eeb6e4c508940a30e94c0032fbd45d677 /tests/ui/auto-traits/typeck-auto-trait-no-supertraits.rs | |
parent | Releasing progress-linux version 1.67.1+dfsg1-1~progress7.99u1. (diff) | |
download | rustc-218caa410aa38c29984be31a5229b9fa717560ee.tar.xz rustc-218caa410aa38c29984be31a5229b9fa717560ee.zip |
Merging upstream version 1.68.2+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'tests/ui/auto-traits/typeck-auto-trait-no-supertraits.rs')
-rw-r--r-- | tests/ui/auto-traits/typeck-auto-trait-no-supertraits.rs | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/tests/ui/auto-traits/typeck-auto-trait-no-supertraits.rs b/tests/ui/auto-traits/typeck-auto-trait-no-supertraits.rs new file mode 100644 index 000000000..2a76893fe --- /dev/null +++ b/tests/ui/auto-traits/typeck-auto-trait-no-supertraits.rs @@ -0,0 +1,39 @@ +// This test is for #29859, we need to ensure auto traits, +// (also known previously as default traits), do not have +// supertraits. Since the compiler synthesizes these +// instances on demand, we are essentially enabling +// users to write axioms if we view trait selection, +// as a proof system. +// +// For example the below test allows us to add the rule: +// forall (T : Type), T : Copy +// +// Providing a copy instance for *any* type, which +// is most definitely unsound. Imagine copying a +// type that contains a mutable reference, enabling +// mutable aliasing. +// +// You can imagine an even more dangerous test, +// which currently compiles on nightly. +// +// fn main() { +// let mut i = 10; +// let (a, b) = copy(&mut i); +// println!("{:?} {:?}", a, b); +// } + +#![feature(auto_traits)] +#![feature(negative_impls)] + +auto trait Magic: Copy {} //~ ERROR E0568 +impl<T:Magic> Magic for T {} + +fn copy<T: Magic>(x: T) -> (T, T) { (x, x) } + +#[derive(Debug)] +struct NoClone; + +fn main() { + let (a, b) = copy(NoClone); + println!("{:?} {:?}", a, b); +} |