7c2012d0ec
Support ?Trait bounds in supertraits and dyn Trait under a feature gate This patch allows `maybe` polarity bounds under a feature gate. The only language change here is that corresponding hard errors are replaced by feature gates. Example: ```rust #![feature(allow_maybe_polarity)] ... trait Trait1 : ?Trait { ... } // ok fn foo(_: Box<(dyn Trait2 + ?Trait)>) {} // ok fn bar<T: ?Sized + ?Trait>(_: &T) {} // ok ``` Maybe bounds still don't do anything (except for `Sized` trait), however this patch will allow us to [experiment with default auto traits](https://github.com/rust-lang/rust/pull/120706#issuecomment-1934006762). This is a part of the [MCP: Low level components for async drop](https://github.com/rust-lang/compiler-team/issues/727) |
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Cargo.toml |