mirror of https://github.com/rust-lang/rust
127 lines
6.0 KiB
Plaintext
127 lines
6.0 KiB
Plaintext
error[E0038]: the trait `NotObjectSafe` cannot be made into an object
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:21:13
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LL | fn car() -> dyn NotObjectSafe {
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| ^^^^^^^^^^^^^^^^^ `NotObjectSafe` cannot be made into an object
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note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:3:8
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LL | trait NotObjectSafe {
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| ------------- this trait cannot be made into an object...
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LL | fn foo() -> Self;
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| ^^^ ...because associated function `foo` has no `self` parameter
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= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `NotObjectSafe` for this new enum and using it instead:
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A
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B
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help: consider turning `foo` into a method by giving it a `&self` argument
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LL | fn foo(&self) -> Self;
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| +++++
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help: alternatively, consider constraining `foo` so it does not apply to trait objects
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LL | fn foo() -> Self where Self: Sized;
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| +++++++++++++++++
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error[E0038]: the trait `NotObjectSafe` cannot be made into an object
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:29:17
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LL | fn cat() -> Box<dyn NotObjectSafe> {
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| ^^^^^^^^^^^^^^^^^ `NotObjectSafe` cannot be made into an object
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note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:3:8
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LL | trait NotObjectSafe {
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| ------------- this trait cannot be made into an object...
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LL | fn foo() -> Self;
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| ^^^ ...because associated function `foo` has no `self` parameter
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= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `NotObjectSafe` for this new enum and using it instead:
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A
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B
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help: consider turning `foo` into a method by giving it a `&self` argument
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LL | fn foo(&self) -> Self;
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| +++++
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help: alternatively, consider constraining `foo` so it does not apply to trait objects
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LL | fn foo() -> Self where Self: Sized;
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| +++++++++++++++++
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error[E0746]: return type cannot have an unboxed trait object
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:21:13
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LL | fn car() -> dyn NotObjectSafe {
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| ^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
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help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
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LL | fn car() -> impl NotObjectSafe {
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| ~~~~
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help: box the return type, and wrap all of the returned values in `Box::new`
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LL ~ fn car() -> Box<dyn NotObjectSafe> {
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LL |
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LL | if true {
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LL ~ return Box::new(A);
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LL | }
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LL ~ Box::new(B)
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error[E0038]: the trait `NotObjectSafe` cannot be made into an object
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:31:16
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LL | return Box::new(A);
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| ^^^^^^^^^^^ `NotObjectSafe` cannot be made into an object
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note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:3:8
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LL | trait NotObjectSafe {
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| ------------- this trait cannot be made into an object...
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LL | fn foo() -> Self;
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| ^^^ ...because associated function `foo` has no `self` parameter
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= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `NotObjectSafe` for this new enum and using it instead:
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A
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B
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= note: required for the cast from `Box<A>` to `Box<(dyn NotObjectSafe + 'static)>`
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help: consider turning `foo` into a method by giving it a `&self` argument
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LL | fn foo(&self) -> Self;
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| +++++
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help: alternatively, consider constraining `foo` so it does not apply to trait objects
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LL | fn foo() -> Self where Self: Sized;
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| +++++++++++++++++
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error[E0038]: the trait `NotObjectSafe` cannot be made into an object
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:33:5
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LL | Box::new(B)
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| ^^^^^^^^^^^ `NotObjectSafe` cannot be made into an object
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note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
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--> $DIR/object-unsafe-trait-in-return-position-dyn-trait.rs:3:8
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LL | trait NotObjectSafe {
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| ------------- this trait cannot be made into an object...
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LL | fn foo() -> Self;
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| ^^^ ...because associated function `foo` has no `self` parameter
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= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `NotObjectSafe` for this new enum and using it instead:
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A
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B
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= note: required for the cast from `Box<B>` to `Box<(dyn NotObjectSafe + 'static)>`
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help: consider turning `foo` into a method by giving it a `&self` argument
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LL | fn foo(&self) -> Self;
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| +++++
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help: alternatively, consider constraining `foo` so it does not apply to trait objects
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LL | fn foo() -> Self where Self: Sized;
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| +++++++++++++++++
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error: aborting due to 5 previous errors
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Some errors have detailed explanations: E0038, E0746.
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For more information about an error, try `rustc --explain E0038`.
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