Incoming breakage: Remove unnecessary ?Sized bound
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Hello there 👋, I'm a member of the Rust compiler team.
?Sizedbounds in associated type bounds don't have any effect. The boundDeref<Target: ?Sized>can simply be replaced withDerefwithout any change in semantics (Targetis already maybe-sized since it's defined liketype Target: ?Sized;in the std library; writingDerefdoesn't implicitly add aSizedrequirement, nor does writingDeref<Target:>(sic!)).It's a bug in the current version of the Rust compiler that writing
TraitRef<AssocTy: ?Sized>is allowed, it should've been forbidden all along. See also rust-lang/rust#135229. The compiler bug is about to be fixed (rust-lang/rust#135331) and these relaxed bounds will soon become a hard error in this position! I sincerely apologize for the inconvenience!This future breakage was found with the help of crater (see the build log).