mirror of https://github.com/rust-lang/rust
57 lines
1.6 KiB
Rust
57 lines
1.6 KiB
Rust
// Test a case where you have an impl of `Foo<X>` for all `X` that
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// is being applied to `for<'a> Foo<&'a mut X>`. Issue #19730.
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trait Foo<X> {
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fn foo(&mut self, x: X) {}
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}
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trait Bar<X> {
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fn bar(&mut self, x: X) {}
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}
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impl<'a, X, F> Foo<X> for &'a mut F where F: Foo<X> + Bar<X> {}
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impl<'a, X, F> Bar<X> for &'a mut F where F: Bar<X> {}
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fn no_hrtb<'b, T>(mut t: T) //~ WARN function cannot return
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where
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T: Bar<&'b isize>,
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{
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// OK -- `T : Bar<&'b isize>`, and thus the impl above ensures that
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// `&mut T : Bar<&'b isize>`.
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no_hrtb(&mut t);
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}
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fn bar_hrtb<T>(mut t: T) //~ WARN function cannot return
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where
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T: for<'b> Bar<&'b isize>,
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{
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// OK -- `T : for<'b> Bar<&'b isize>`, and thus the impl above
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// ensures that `&mut T : for<'b> Bar<&'b isize>`. This is an
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// example of a "perfect forwarding" impl.
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bar_hrtb(&mut t);
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}
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fn foo_hrtb_bar_not<'b, T>(mut t: T) //~ WARN function cannot return
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where
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T: for<'a> Foo<&'a isize> + Bar<&'b isize>,
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{
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// Not OK -- The forwarding impl for `Foo` requires that `Bar` also
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// be implemented. Thus to satisfy `&mut T : for<'a> Foo<&'a
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// isize>`, we require `T : for<'a> Bar<&'a isize>`, but the where
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// clause only specifies `T : Bar<&'b isize>`.
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foo_hrtb_bar_not(&mut t);
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//~^ ERROR implementation of `Bar` is not general enough
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//~^^ ERROR lifetime may not live long enough
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}
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fn foo_hrtb_bar_hrtb<T>(mut t: T) //~ WARN function cannot return
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where
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T: for<'a> Foo<&'a isize> + for<'b> Bar<&'b isize>,
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{
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// OK -- now we have `T : for<'b> Bar<&'b isize>`.
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foo_hrtb_bar_hrtb(&mut t);
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}
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fn main() {}
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