diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /src/test/ui/hrtb/issue-46989.rs | |
parent | Initial commit. (diff) | |
download | rustc-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/issue-46989.rs')
-rw-r--r-- | src/test/ui/hrtb/issue-46989.rs | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/src/test/ui/hrtb/issue-46989.rs b/src/test/ui/hrtb/issue-46989.rs new file mode 100644 index 000000000..4a09f4be1 --- /dev/null +++ b/src/test/ui/hrtb/issue-46989.rs @@ -0,0 +1,40 @@ +// Regression test for #46989: +// +// In the move to universes, this test started passing. +// It is not necessarily WRONG to do so, but it was a bit +// surprising. The reason that it passed is that when we were +// asked to prove that +// +// for<'a> fn(&'a i32): Foo +// +// we were able to use the impl below to prove +// +// fn(&'empty i32): Foo +// +// and then we were able to prove that +// +// fn(&'empty i32) = for<'a> fn(&'a i32) +// +// This last fact is somewhat surprising, but essentially "falls out" +// from handling variance correctly. In particular, consider the subtyping +// relations. First: +// +// fn(&'empty i32) <: for<'a> fn(&'a i32) +// +// This holds because -- intuitively -- a fn that takes a reference but doesn't use +// it can be given a reference with any lifetime. Similarly, the opposite direction: +// +// for<'a> fn(&'a i32) <: fn(&'empty i32) +// +// holds because 'a can be instantiated to 'empty. + +trait Foo {} + +impl<A> Foo for fn(A) {} + +fn assert_foo<T: Foo>() {} + +fn main() { + assert_foo::<fn(&i32)>(); + //~^ ERROR implementation of `Foo` is not general enough +} |