Update comments re type parameter hack in object safety #65850
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To check if a method's receiver type is object safe, we create a new receiver type by substituting in a bogus type parameter (let's call it `U`) for `Self`, and checking that the unmodified receiver type implements `DispatchFromDyn<receiver type with Self = U>`. It would be better to use `dyn Trait` directly, and the only reason we don't is because it triggers another check that `Trait` is object safe, resulting in a query cycle. Once the feature `object_safe_for_dispatch` (tracking issue rust-lang#43561) is stabilized, this will no longer be the case, and we'll be able to use `dyn Trait` as the unsized `Self` type. I've updated the comments in object_safety.rs accordingly.
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Update comments re type parameter hack in object safety To check if a method's receiver type is object safe, we create a new receiver type by substituting in a bogus type parameter (let's call it `U`) for `Self`, and checking that the unmodified receiver type implements `DispatchFromDyn<receiver type with Self = U>`. It would be better to use `dyn Trait` directly, and the only reason we don't is because it triggers another check that `Trait` is object safe, resulting in a query cycle. Once the feature `object_safe_for_dispatch` (tracking issue rust-lang#43561) is stabilized, this will no longer be the case, and we'll be able to use `dyn Trait` as the unsized `Self` type. I've updated the comments in object_safety.rs accordingly. cc @Centril @nikomatsakis @bovinebuddha
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Update comments re type parameter hack in object safety To check if a method's receiver type is object safe, we create a new receiver type by substituting in a bogus type parameter (let's call it `U`) for `Self`, and checking that the unmodified receiver type implements `DispatchFromDyn<receiver type with Self = U>`. It would be better to use `dyn Trait` directly, and the only reason we don't is because it triggers another check that `Trait` is object safe, resulting in a query cycle. Once the feature `object_safe_for_dispatch` (tracking issue rust-lang#43561) is stabilized, this will no longer be the case, and we'll be able to use `dyn Trait` as the unsized `Self` type. I've updated the comments in object_safety.rs accordingly. cc @Centril @nikomatsakis @bovinebuddha
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Update comments re type parameter hack in object safety To check if a method's receiver type is object safe, we create a new receiver type by substituting in a bogus type parameter (let's call it `U`) for `Self`, and checking that the unmodified receiver type implements `DispatchFromDyn<receiver type with Self = U>`. It would be better to use `dyn Trait` directly, and the only reason we don't is because it triggers another check that `Trait` is object safe, resulting in a query cycle. Once the feature `object_safe_for_dispatch` (tracking issue rust-lang#43561) is stabilized, this will no longer be the case, and we'll be able to use `dyn Trait` as the unsized `Self` type. I've updated the comments in object_safety.rs accordingly. cc @Centril @nikomatsakis @bovinebuddha
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Rollup of 7 pull requests Successful merges: - #65274 (Upload toolstates.json to rust-lang-ci2) - #65434 (Add long error explanation for E0577) - #65850 (Update comments re type parameter hack in object safety) - #65955 (ci: revert msys2 ca-certificates hack) - #65959 (Fix an incorrect docstring for Immediate in librustc_mir/interpret.) - #65979 (Switch CrateMetadata's source_map_import_info from RwLock to Once) - #65981 (work around aggressive syntax feature gating) Failed merges: r? @ghost
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To check if a method's receiver type is object safe, we create a new receiver type by substituting in a bogus type parameter (let's call it
U) forSelf, and checking that the unmodified receiver type implementsDispatchFromDyn<receiver type with Self = U>. It would be better to usedyn Traitdirectly, and the only reason we don't is because it triggers another check thatTraitis object safe, resulting in a query cycle. Once the featureobject_safe_for_dispatch(tracking issue #43561) is stabilized, this will no longer be the case, and we'll be able to usedyn Traitas the unsizedSelftype. I've updated the comments in object_safety.rs accordingly.cc @Centril @nikomatsakis @bovinebuddha