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

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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The documentation given for the trait is outdated: *all* function pointers implement `PartialEq` and `Eq` these days.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
This commit is contained in:
bors 2024-01-26 00:17:00 +00:00
commit dd2559e08e
76 changed files with 273 additions and 536 deletions
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2
compiler/rustc_const_eval/src/const_eval/valtrees.rs
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@ -138,7 +138,7 @@ pub(crate) fn const_to_valtree_inner<'tcx>(
}
// Trait objects are not allowed in type level constants, as we have no concept for
// resolving their backing type, even if we can do that at const eval time. We may
// hypothetically be able to allow `dyn StructuralEq` trait objects in the future,
// hypothetically be able to allow `dyn StructuralPartialEq` trait objects in the future,
// but it is unclear if this is useful.
ty::Dynamic(..) => Err(ValTreeCreationError::NonSupportedType),