Unsoundness due to where clauses not checked for well-formedness #98117
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This code does pass: (playground)
trait Outlives<'a>: 'a {} // without `: 'a`, it fails as expected. fn t_is_static<T>() where &'static T: Outlives<'static>, { }But according to RFC 1214 functions are responsible for checking the well-formedness of their own where clauses. So this should fail and require an explicit bound T: 'static.
Here is an exploit of this unsoundness: (playground)
trait Outlives<'a>: 'a {} impl<'a, T> Outlives<'a> for &'a T {} fn step2<T>(t: T) -> &'static str where &'static T: Outlives<'static>, T: AsRef<str>, { AsRef::as_ref(Box::leak(Box::new(t) as Box<dyn AsRef<str> + 'static>)) } fn step1<T>(t: T) -> &'static str where for<'a> &'a T: Outlives<'a>, T: AsRef<str>, { step2(t) } fn main() { let s: &'static str = step1(&String::from("blah blah blah")); println!("{s}"); }@rustbot label C-bug T-compiler T-types A-lifetimes I-unsound
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Area: Lifetimes / regionsCategory: This is a bug.Issue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/SoundnessHigh priorityStatus: This bug is tracked inside the repo by a `known-bug` test.Relevant to the compiler team, which will review and decide on the PR/issue.Relevant to the types team, which will review and decide on the PR/issue.
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