45 lines
1.0 KiB
Rust
45 lines
1.0 KiB
Rust
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//@ known-bug: #110534
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//@ edition:2021
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use core::cell::Ref;
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struct System;
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trait IntoSystem {
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fn into_system(self) -> System;
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}
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impl IntoSystem for fn(Ref<'_, u32>) {
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fn into_system(self) -> System { System }
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}
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impl<A> IntoSystem for fn(A)
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where
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// n.b. No `Ref<'_, u32>` can satisfy this bound
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A: 'static + for<'x> MaybeBorrowed<'x, Output = A>,
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{
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fn into_system(self) -> System { System }
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}
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//---------------------------------------------------
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trait MaybeBorrowed<'a> {
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type Output: 'a;
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}
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// If you comment this out you'll see the compiler chose to look at the
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// fn(A) implementation of IntoSystem above
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impl<'a, 'b> MaybeBorrowed<'a> for Ref<'b, u32> {
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type Output = Ref<'a, u32>;
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}
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// ---------------------------------------------
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fn main() {
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fn sys_ref(_age: Ref<u32>) {}
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let _sys_c = (sys_ref as fn(_)).into_system();
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// properly fails
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// let _sys_c = (sys_ref as fn(Ref<'static, u32>)).into_system();
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// properly succeeds
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// let _sys_c = (sys_ref as fn(Ref<'_, u32>)).into_system();
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}
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