Auto merge of #116493 - compiler-errors:coinductive-cycle-lint, r=lcnr

Bump `COINDUCTIVE_OVERLAP_IN_COHERENCE` to deny + warn in deps

1.73 is the first place this shows up in stable (recall that there was only 1 regression), so let's bump this to deny on nightly.

r? lcnr

compiler/rustc_lint_defs/src/builtin.rs

@@ -4449,11 +4449,11 @@ declare_lint! {
     /// on itself), the blanket impl is not considered to hold for `u8`. This will
     /// change in a future release.
     pub COINDUCTIVE_OVERLAP_IN_COHERENCE,
-    Warn,
+    Deny,
     "impls that are not considered to overlap may be considered to \
     overlap in the future",
     @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
         reference: "issue #114040 <https://github.com/rust-lang/rust/issues/114040>",
     };
 }

tests/ui/coherence/warn-when-cycle-is-error-in-coherence.stderr

@@ -24,3 +24,23 @@ LL | #![deny(coinductive_overlap_in_coherence)]
 
 error: aborting due to previous error
 
+Future incompatibility report: Future breakage diagnostic:
+error: implementations of `PartialEq<Interval<_>>` for `Interval<_>` will conflict in the future
+  --> $DIR/warn-when-cycle-is-error-in-coherence.rs:13:1
+   |
+LL | #[derive(PartialEq, Default)]
+   |          --------- the second impl is here
+...
+LL | impl<T, Q> PartialEq<Q> for Interval<T>
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the first impl is here
+   |
+   = 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 #114040 <https://github.com/rust-lang/rust/issues/114040>
+   = note: impls that are not considered to overlap may be considered to overlap in the future
+   = note: `Interval<_>: PartialOrd` may be considered to hold in future releases, causing the impls to overlap
+note: the lint level is defined here
+  --> $DIR/warn-when-cycle-is-error-in-coherence.rs:1:9
+   |
+LL | #![deny(coinductive_overlap_in_coherence)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+