41 lines
962 B
Rust
41 lines
962 B
Rust
#![crate_type = "lib"]
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#![feature(specialization)]
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#![feature(unsize, coerce_unsized)]
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#![allow(incomplete_features)]
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use std::ops::CoerceUnsized;
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pub struct SmartassPtr<A: Smartass+?Sized>(A::Data);
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pub trait Smartass {
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type Data;
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type Data2: CoerceUnsized<*const [u8]>;
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}
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pub trait MaybeDynCompatible {}
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impl MaybeDynCompatible for () {}
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impl<T> Smartass for T {
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type Data = <Self as Smartass>::Data2;
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default type Data2 = ();
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//~^ ERROR: the trait bound `(): CoerceUnsized<*const [u8]>` is not satisfied
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}
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impl Smartass for () {
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type Data2 = *const [u8; 1];
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}
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impl Smartass for dyn MaybeDynCompatible {
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type Data = *const [u8];
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type Data2 = *const [u8; 0];
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}
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impl<U: Smartass+?Sized, T: Smartass+?Sized> CoerceUnsized<SmartassPtr<T>> for SmartassPtr<U>
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where <U as Smartass>::Data: std::ops::CoerceUnsized<<T as Smartass>::Data>
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{}
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pub fn conv(s: SmartassPtr<()>) -> SmartassPtr<dyn MaybeDynCompatible> {
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s
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}
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