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add feature gate tests for DispatchFromDyn
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dimpolo committed Jan 24, 2023

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9 changes: 9 additions & 0 deletions tests/ui/feature-gates/feature-gate-dispatch-from-dyn-cell.rs
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// Check that even though Cell: DispatchFromDyn it remains an invalid self parameter type

use std::cell::Cell;

trait Trait{
fn cell(self: Cell<&Self>); //~ ERROR invalid `self` parameter type: Cell<&Self>
}

fn main() {}
12 changes: 12 additions & 0 deletions tests/ui/feature-gates/feature-gate-dispatch-from-dyn-cell.stderr
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error[E0307]: invalid `self` parameter type: Cell<&Self>
--> $DIR/feature-gate-dispatch-from-dyn-cell.rs:6:19
|
LL | fn cell(self: Cell<&Self>);
| ^^^^^^^^^^^
|
= note: type of `self` must be `Self` or a type that dereferences to it
= help: consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one of the previous types except `Self`)

error: aborting due to previous error

For more information about this error, try `rustc --explain E0307`.
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// Check that a self parameter type requires a DispatchFromDyn impl to be object safe

#![feature(arbitrary_self_types, unsize, coerce_unsized)]

use std::{
marker::Unsize,
ops::{CoerceUnsized, Deref},
};

struct Ptr<T: ?Sized>(Box<T>);

impl<T: ?Sized> Deref for Ptr<T> {
type Target = T;

fn deref(&self) -> &T {
&*self.0
}
}

impl<T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<Ptr<U>> for Ptr<T> {}
// Because this impl is missing the coercion below fails.
// impl<T: Unsize<U> + ?Sized, U: ?Sized> DispatchFromDyn<Ptr<U>> for Ptr<T> {}

trait Trait {
fn ptr(self: Ptr<Self>);
}
impl Trait for i32 {
fn ptr(self: Ptr<Self>) {}
}

fn main() {
Ptr(Box::new(4)) as Ptr<dyn Trait>;
//~^ ERROR the trait `Trait` cannot be made into an object
//~^^ ERROR the trait `Trait` cannot be made into an object
}
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error[E0038]: the trait `Trait` cannot be made into an object
--> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:32:25
|
LL | fn ptr(self: Ptr<Self>);
| --------- help: consider changing method `ptr`'s `self` parameter to be `&self`: `&Self`
...
LL | Ptr(Box::new(4)) as Ptr<dyn Trait>;
| ^^^^^^^^^^^^^^ `Trait` cannot be made into an object
|
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>
--> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:25:18
|
LL | trait Trait {
| ----- this trait cannot be made into an object...
LL | fn ptr(self: Ptr<Self>);
| ^^^^^^^^^ ...because method `ptr`'s `self` parameter cannot be dispatched on

error[E0038]: the trait `Trait` cannot be made into an object
--> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:32:5
|
LL | fn ptr(self: Ptr<Self>);
| --------- help: consider changing method `ptr`'s `self` parameter to be `&self`: `&Self`
...
LL | Ptr(Box::new(4)) as Ptr<dyn Trait>;
| ^^^^^^^^^^^^^^^^ `Trait` cannot be made into an object
|
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>
--> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:25:18
|
LL | trait Trait {
| ----- this trait cannot be made into an object...
LL | fn ptr(self: Ptr<Self>);
| ^^^^^^^^^ ...because method `ptr`'s `self` parameter cannot be dispatched on
note: required for `Ptr<{integer}>` to implement `CoerceUnsized<Ptr<dyn Trait>>`
--> $DIR/feature-gate-dispatch-from-dyn-missing-impl.rs:20:40
|
LL | impl<T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<Ptr<U>> for Ptr<T> {}
| --------- ^^^^^^^^^^^^^^^^^^^^^ ^^^^^^
| |
| unsatisfied trait bound introduced here
= note: required by cast to type `Ptr<dyn Trait>`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0038`.

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