Rollup merge of #102635 - lcnr:incoherent_auto_trait_objects, r=jackh726

make `order_dependent_trait_objects` show up in future-breakage reports

tried to change it to a hard error in #102474 but breaking the more than 1000 dependents of `traitobject` doesn't feel great :sweat_smile:

This lint has existed since more than 3 years now and the way this is currently implemented is buggy and will break with #102472. imo we should upgrade it to also report for dependencies and maybe also backport this to beta. Then after maybe 2-3 stable versions I would like to finally convert this lint to a hard error.

3 files changed, 112 insertions, 0 deletions

diff --git a/src/test/ui/lint/lint-incoherent-auto-trait-objects.stderr b/src/test/ui/lint/lint-incoherent-auto-trait-objects.stderr
index 3f366bedbf3..2cc4d382d9d 100644
--- a/src/test/ui/lint/lint-incoherent-auto-trait-objects.stderr
+++ b/src/test/ui/lint/lint-incoherent-auto-trait-objects.stderr
@@ -37,3 +37,45 @@ LL | impl Foo for dyn Send + Sync + Send {}
 
 error: aborting due to 3 previous errors
 
+Future incompatibility report: Future breakage diagnostic:
+error: conflicting implementations of trait `Foo` for type `(dyn std::marker::Send + 'static)`: (E0119)
+  --> $DIR/lint-incoherent-auto-trait-objects.rs:5:1
+   |
+LL | impl Foo for dyn Send {}
+   | --------------------- first implementation here
+LL |
+LL | impl Foo for dyn Send + Send {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + 'static)`
+   |
+   = 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 #56484 <https://github.com/rust-lang/rust/issues/56484>
+   = note: `#[deny(order_dependent_trait_objects)]` on by default
+
+Future breakage diagnostic:
+error: conflicting implementations of trait `Foo` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`: (E0119)
+  --> $DIR/lint-incoherent-auto-trait-objects.rs:11:1
+   |
+LL | impl Foo for dyn Send + Sync {}
+   | ---------------------------- first implementation here
+LL |
+LL | impl Foo for dyn Sync + Send {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
+   |
+   = 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 #56484 <https://github.com/rust-lang/rust/issues/56484>
+   = note: `#[deny(order_dependent_trait_objects)]` on by default
+
+Future breakage diagnostic:
+error: conflicting implementations of trait `Foo` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`: (E0119)
+  --> $DIR/lint-incoherent-auto-trait-objects.rs:15:1
+   |
+LL | impl Foo for dyn Sync + Send {}
+   | ---------------------------- first implementation here
+...
+LL | impl Foo for dyn Send + Sync + Send {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
+   |
+   = 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 #56484 <https://github.com/rust-lang/rust/issues/56484>
+   = note: `#[deny(order_dependent_trait_objects)]` on by default
+
diff --git a/src/test/ui/traits/issue-33140-hack-boundaries.stderr b/src/test/ui/traits/issue-33140-hack-boundaries.stderr
index 62cfca545b2..58286648d4f 100644
--- a/src/test/ui/traits/issue-33140-hack-boundaries.stderr
+++ b/src/test/ui/traits/issue-33140-hack-boundaries.stderr
@@ -66,3 +66,20 @@ error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0119, E0751.
 For more information about an error, try `rustc --explain E0119`.
+Future incompatibility report: Future breakage diagnostic:
+warning: conflicting implementations of trait `Trait0` for type `(dyn std::marker::Send + 'static)`: (E0119)
+  --> $DIR/issue-33140-hack-boundaries.rs:10:1
+   |
+LL | impl Trait0 for dyn Send {}
+   | ------------------------ first implementation here
+LL | impl Trait0 for dyn Send {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + 'static)`
+   |
+   = 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 #56484 <https://github.com/rust-lang/rust/issues/56484>
+note: the lint level is defined here
+  --> $DIR/issue-33140-hack-boundaries.rs:2:10
+   |
+LL | #![allow(order_dependent_trait_objects)]
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
diff --git a/src/test/ui/traits/object/issue-33140-traitobject-crate.stderr b/src/test/ui/traits/object/issue-33140-traitobject-crate.stderr
index 4ab777bd4df..0af4df2aecb 100644
--- a/src/test/ui/traits/object/issue-33140-traitobject-crate.stderr
+++ b/src/test/ui/traits/object/issue-33140-traitobject-crate.stderr
@@ -40,3 +40,56 @@ LL | unsafe impl Trait for dyn (::std::marker::Sync) + Send + Sync { }
 
 warning: 3 warnings emitted
 
+Future incompatibility report: Future breakage diagnostic:
+warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`: (E0119)
+  --> $DIR/issue-33140-traitobject-crate.rs:86:1
+   |
+LL | unsafe impl Trait for dyn (::std::marker::Send) + Sync { }
+   | ------------------------------------------------------ first implementation here
+LL | unsafe impl Trait for dyn (::std::marker::Send) + Send + Sync { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
+   |
+   = 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 #56484 <https://github.com/rust-lang/rust/issues/56484>
+note: the lint level is defined here
+  --> $DIR/issue-33140-traitobject-crate.rs:3:9
+   |
+LL | #![warn(order_dependent_trait_objects)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Future breakage diagnostic:
+warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`: (E0119)
+  --> $DIR/issue-33140-traitobject-crate.rs:89:1
+   |
+LL | unsafe impl Trait for dyn (::std::marker::Send) + Send + Sync { }
+   | ------------------------------------------------------------- first implementation here
+...
+LL | unsafe impl Trait for dyn (::std::marker::Sync) + Send { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
+   |
+   = 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 #56484 <https://github.com/rust-lang/rust/issues/56484>
+note: the lint level is defined here
+  --> $DIR/issue-33140-traitobject-crate.rs:3:9
+   |
+LL | #![warn(order_dependent_trait_objects)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Future breakage diagnostic:
+warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`: (E0119)
+  --> $DIR/issue-33140-traitobject-crate.rs:93:1
+   |
+LL | unsafe impl Trait for dyn (::std::marker::Sync) + Send { }
+   | ------------------------------------------------------ first implementation here
+...
+LL | unsafe impl Trait for dyn (::std::marker::Sync) + Send + Sync { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
+   |
+   = 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 #56484 <https://github.com/rust-lang/rust/issues/56484>
+note: the lint level is defined here
+  --> $DIR/issue-33140-traitobject-crate.rs:3:9
+   |
+LL | #![warn(order_dependent_trait_objects)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+