Auto merge of #116167 - RalfJung:structural-eq, r=lcnr

remove StructuralEq trait

The documentation given for the trait is outdated: *all* function pointers implement `PartialEq` and `Eq` these days. So the `StructuralEq` trait doesn't really seem to have any reason to exist any more.

One side-effect of this PR is that we allow matching on some consts that do not implement `Eq`. However, we already allowed matching on floats and consts containing floats, so this is not new, it is just allowed in more cases now. IMO it makes no sense at all to allow float matching but also sometimes require an `Eq` instance. If we want to require `Eq` we should adjust https://github.com/rust-lang/rust/pull/115893 to check for `Eq`, and rule out float matching for good.

Fixes https://github.com/rust-lang/rust/issues/115881

2 files changed, 0 insertions, 17 deletions

diff --git a/tests/ui/crashes/ice-6254.rs b/tests/ui/crashes/ice-6254.rs
index 2ae426cf789..8af60890390 100644
--- a/tests/ui/crashes/ice-6254.rs
+++ b/tests/ui/crashes/ice-6254.rs
@@ -11,8 +11,6 @@ fn main() {
     // This used to cause an ICE (https://github.com/rust-lang/rust/issues/78071)
     match FOO_REF_REF {
         FOO_REF_REF => {},
-        //~^ ERROR: to use a constant of type `Foo` in a pattern, `Foo` must be annotated
-        //~| NOTE: for more information, see issue #62411 <https://github.com/rust-lang/ru
         Foo(_) => {},
     }
 }
diff --git a/tests/ui/crashes/ice-6254.stderr b/tests/ui/crashes/ice-6254.stderr
deleted file mode 100644
index 7a34e6cceee..00000000000
--- a/tests/ui/crashes/ice-6254.stderr
+++ /dev/null
@@ -1,15 +0,0 @@
-error: to use a constant of type `Foo` in a pattern, `Foo` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/ice-6254.rs:13:9
-   |
-LL |         FOO_REF_REF => {},
-   |         ^^^^^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #62411 <https://github.com/rust-lang/rust/issues/62411>
-   = note: the traits must be derived, manual `impl`s are not sufficient
-   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
-   = note: `-D indirect-structural-match` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(indirect_structural_match)]`
-
-error: aborting due to 1 previous error
-