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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
commit698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch)
tree173a775858bd501c378080a10dca74132f05bc50 /src/test/ui/hrtb/hrtb-perfect-forwarding.rs
parentInitial commit. (diff)
downloadrustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz
rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/test/ui/hrtb/hrtb-perfect-forwarding.rs')
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diff --git a/src/test/ui/hrtb/hrtb-perfect-forwarding.rs b/src/test/ui/hrtb/hrtb-perfect-forwarding.rs
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+// Test a case where you have an impl of `Foo<X>` for all `X` that
+// is being applied to `for<'a> Foo<&'a mut X>`. Issue #19730.
+
+trait Foo<X> {
+ fn foo(&mut self, x: X) {}
+}
+
+trait Bar<X> {
+ fn bar(&mut self, x: X) {}
+}
+
+impl<'a, X, F> Foo<X> for &'a mut F where F: Foo<X> + Bar<X> {}
+
+impl<'a, X, F> Bar<X> for &'a mut F where F: Bar<X> {}
+
+fn no_hrtb<'b, T>(mut t: T) //~ WARN function cannot return
+where
+ T: Bar<&'b isize>,
+{
+ // OK -- `T : Bar<&'b isize>`, and thus the impl above ensures that
+ // `&mut T : Bar<&'b isize>`.
+ no_hrtb(&mut t);
+}
+
+fn bar_hrtb<T>(mut t: T) //~ WARN function cannot return
+where
+ T: for<'b> Bar<&'b isize>,
+{
+ // OK -- `T : for<'b> Bar<&'b isize>`, and thus the impl above
+ // ensures that `&mut T : for<'b> Bar<&'b isize>`. This is an
+ // example of a "perfect forwarding" impl.
+ bar_hrtb(&mut t);
+}
+
+fn foo_hrtb_bar_not<'b, T>(mut t: T) //~ WARN function cannot return
+where
+ T: for<'a> Foo<&'a isize> + Bar<&'b isize>,
+{
+ // Not OK -- The forwarding impl for `Foo` requires that `Bar` also
+ // be implemented. Thus to satisfy `&mut T : for<'a> Foo<&'a
+ // isize>`, we require `T : for<'a> Bar<&'a isize>`, but the where
+ // clause only specifies `T : Bar<&'b isize>`.
+ foo_hrtb_bar_not(&mut t);
+ //~^ ERROR implementation of `Bar` is not general enough
+ //~^^ ERROR lifetime may not live long enough
+}
+
+fn foo_hrtb_bar_hrtb<T>(mut t: T) //~ WARN function cannot return
+where
+ T: for<'a> Foo<&'a isize> + for<'b> Bar<&'b isize>,
+{
+ // OK -- now we have `T : for<'b> Bar<&'b isize>`.
+ foo_hrtb_bar_hrtb(&mut t);
+}
+
+fn main() {}