36 lines
852 B
Rust
36 lines
852 B
Rust
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// Check that a self parameter type requires a DispatchFromDyn impl to be object safe
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#![feature(arbitrary_self_types, unsize, coerce_unsized)]
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use std::{
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marker::Unsize,
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ops::{CoerceUnsized, Deref},
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};
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struct Ptr<T: ?Sized>(Box<T>);
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impl<T: ?Sized> Deref for Ptr<T> {
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type Target = T;
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fn deref(&self) -> &T {
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&*self.0
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}
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}
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impl<T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<Ptr<U>> for Ptr<T> {}
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// Because this impl is missing the coercion below fails.
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// impl<T: Unsize<U> + ?Sized, U: ?Sized> DispatchFromDyn<Ptr<U>> for Ptr<T> {}
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trait Trait {
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fn ptr(self: Ptr<Self>);
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}
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impl Trait for i32 {
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fn ptr(self: Ptr<Self>) {}
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}
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fn main() {
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Ptr(Box::new(4)) as Ptr<dyn Trait>;
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//~^ ERROR the trait `Trait` cannot be made into an object
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//~^^ ERROR the trait `Trait` cannot be made into an object
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}
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