rust-lang · compiler-errors · Oct 2, 2023
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
@@ -844,7 +844,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(thir_unsafeck, true);
     tracked!(tiny_const_eval_limit, true);
     tracked!(tls_model, Some(TlsModel::GeneralDynamic));
-    tracked!(trait_solver, TraitSolver::NextCoherence);
+    tracked!(trait_solver, TraitSolver::Next);
     tracked!(translate_remapped_path_to_local_path, false);
     tracked!(trap_unreachable, Some(false));
     tracked!(treat_err_as_bug, NonZeroUsize::new(1));

diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
@@ -1009,7 +1009,7 @@ mod parse {
             Some("next") => *slot = TraitSolver::Next,
             Some("next-coherence") => *slot = TraitSolver::NextCoherence,
             // default trait solver is subject to change..
-            Some("default") => *slot = TraitSolver::Classic,
+            Some("default") => *slot = TraitSolver::NextCoherence,
             _ => return false,
         }
         true
@@ -1830,8 +1830,8 @@ written to standard error output)"),
         "for every macro invocation, print its name and arguments (default: no)"),
     track_diagnostics: bool = (false, parse_bool, [UNTRACKED],
         "tracks where in rustc a diagnostic was emitted"),
-    trait_solver: TraitSolver = (TraitSolver::Classic, parse_trait_solver, [TRACKED],
-        "specify the trait solver mode used by rustc (default: classic)"),
+    trait_solver: TraitSolver = (TraitSolver::NextCoherence, parse_trait_solver, [TRACKED],
+        "specify the trait solver mode used by rustc (default: next-coherence)"),
     // Diagnostics are considered side-effects of a query (see `QuerySideEffects`) and are saved
     // alongside query results and changes to translation options can affect diagnostics - so
     // translation options should be tracked.

diff --git a/tests/ui/associated-types/associated-types-coherence-failure.stderr b/tests/ui/associated-types/associated-types-coherence-failure.stderr
@@ -1,20 +1,20 @@
-error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `Cow<'_, _>`
+error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `<_ as ToOwned>::Owned`
   --> $DIR/associated-types-coherence-failure.rs:21:1
    |
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwned {
    | ------------------------------------------------------------ first implementation here
 ...
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for Cow<'a, B> where B: ToOwned {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Cow<'_, _>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<_ as ToOwned>::Owned`
 
-error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `&_`
+error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `<_ as ToOwned>::Owned`
   --> $DIR/associated-types-coherence-failure.rs:28:1
    |
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwned {
    | ------------------------------------------------------------ first implementation here
 ...
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for &'a B where B: ToOwned {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<_ as ToOwned>::Owned`
 
 error: aborting due to 2 previous errors
 

diff --git a/tests/ui/coherence/coherence-negative-outlives-lifetimes.stock.stderr b/tests/ui/coherence/coherence-negative-outlives-lifetimes.stock.stderr
@@ -5,6 +5,8 @@ LL | impl<'a, T: MyPredicate<'a>> MyTrait<'a> for T {}
    | ---------------------------------------------- first implementation here
 LL | impl<'a, T> MyTrait<'a> for &'a T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   |
+   = note: downstream crates may implement trait `MyPredicate<'_>` for type `&_`
 
 error: aborting due to previous error
 

diff --git a/tests/ui/coherence/coherence-overlap-negate-not-use-feature-gate.stderr b/tests/ui/coherence/coherence-overlap-negate-not-use-feature-gate.stderr
@@ -5,6 +5,8 @@ LL | impl<T: DerefMut> Foo for T {}
    | --------------------------- first implementation here
 LL | impl<U> Foo for &U {}
    | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   |
+   = note: downstream crates may implement trait `std::ops::DerefMut` for type `&_`
 
 error: aborting due to previous error
 

diff --git a/tests/ui/coherence/warn-when-cycle-is-error-in-coherence.stderr b/tests/ui/coherence/warn-when-cycle-is-error-in-coherence.stderr
@@ -1,21 +1,14 @@
-error: implementations of `PartialEq<Interval<_>>` for `Interval<_>` will conflict in the future
-  --> $DIR/warn-when-cycle-is-error-in-coherence.rs:13:1
+error[E0119]: conflicting implementations of trait `PartialEq<Interval<_>>` for type `Interval<_>`
+  --> $DIR/warn-when-cycle-is-error-in-coherence.rs:7:10
    |
 LL | #[derive(PartialEq, Default)]
-   |          --------- the second impl is here
+   |          ^^^^^^^^^ conflicting implementation for `Interval<_>`
 ...
 LL | impl<T, Q> PartialEq<Q> for Interval<T>
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the first impl is here
+   | --------------------------------------- first implementation 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)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in the derive macro `PartialEq` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0119`.
diff --git a/tests/ui/error-codes/E0476.stderr b/tests/ui/error-codes/E0476.stderr
@@ -1,3 +1,7 @@
+WARN rustc_trait_selection::traits::coherence expected an unknowable trait ref: <Wrapper<_> as std::marker::Unsize<Wrapper<_>>>
+WARN rustc_trait_selection::traits::coherence expected an unknowable trait ref: <Wrapper<_> as std::marker::Unsize<Wrapper<_>>>
+WARN rustc_trait_selection::traits::coherence expected an unknowable trait ref: <Wrapper<_> as std::marker::Unsize<Wrapper<_>>>
+WARN rustc_trait_selection::traits::coherence expected an unknowable trait ref: <Wrapper<_> as std::marker::Unsize<Wrapper<_>>>
 error[E0119]: conflicting implementations of trait `CoerceUnsized<&Wrapper<_>>` for type `&Wrapper<_>`
   --> $DIR/E0476.rs:9:1
    |

diff --git a/tests/ui/error-codes/e0119/issue-23563.stderr b/tests/ui/error-codes/e0119/issue-23563.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `LolFrom<&[_]>` for type `LocalType<_>`
+error[E0119]: conflicting implementations of trait `LolFrom<&[u8]>` for type `LocalType<u8>`
   --> $DIR/issue-23563.rs:13:1
    |
 LL | impl<'a, T> LolFrom<&'a [T]> for LocalType<T> {

diff --git a/tests/ui/feature-gates/feature-gate-with_negative_coherence.stderr b/tests/ui/feature-gates/feature-gate-with_negative_coherence.stderr
@@ -6,6 +6,8 @@ LL | impl<T: std::ops::DerefMut> Foo for T { }
 LL |
 LL | impl<T> Foo for &T { }
    | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   |
+   = note: downstream crates may implement trait `std::ops::DerefMut` for type `&_`
 
 error: aborting due to previous error
 

diff --git a/tests/ui/impl-trait/negative-reasoning.stderr b/tests/ui/impl-trait/negative-reasoning.stderr
@@ -6,8 +6,6 @@ LL | impl<T: std::fmt::Debug> AnotherTrait for T {}
 ...
 LL | impl AnotherTrait for D<OpaqueType> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `D<OpaqueType>`
-   |
-   = note: upstream crates may add a new impl of trait `std::fmt::Debug` for type `OpaqueType` in future versions
 
 error: aborting due to previous error
 

diff --git a/tests/ui/never_type/never-from-impl-is-reserved.stderr b/tests/ui/never_type/never-from-impl-is-reserved.stderr
@@ -6,8 +6,6 @@ LL | impl MyTrait for MyFoo {}
 LL | // This will conflict with the first impl if we impl `for<T> T: From<!>`.
 LL | impl<T> MyTrait for T where T: From<!> {}
    | ^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MyFoo`
-   |
-   = note: permitting this impl would forbid us from adding `impl<T> From<!> for T` later; see rust-lang/rust#64715 for details
 
 error: aborting due to previous error
 

diff --git a/tests/ui/traits/issue-105231.stderr b/tests/ui/traits/issue-105231.stderr
@@ -14,16 +14,15 @@ LL |
 LL ~ struct B<T>(Box<A<A<T>>>);
    |
 
-error[E0275]: overflow evaluating the requirement `A<A<A<A<A<A<A<...>>>>>>>: Send`
+error[E0119]: conflicting implementations of trait `Foo` for type `B<u8>`
+  --> $DIR/issue-105231.rs:7:1
    |
-   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_105231`)
-note: required because it appears within the type `B<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<A<u8>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
-  --> $DIR/issue-105231.rs:4:8
-   |
-LL | struct B<T>(A<A<T>>);
-   |        ^
+LL | impl<T> Foo for T where T: Send {}
+   | ----------------- first implementation here
+LL | impl Foo for B<u8> {}
+   | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `B<u8>`
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0072, E0275.
+Some errors have detailed explanations: E0072, E0119.
 For more information about an error, try `rustc --explain E0072`.
diff --git a/tests/ui/traits/reservation-impl/coherence-conflict.old.stderr b/tests/ui/traits/reservation-impl/coherence-conflict.old.stderr
@@ -5,8 +5,6 @@ LL | impl OtherTrait for () {}
    | ---------------------- first implementation here
 LL | impl<T: MyTrait> OtherTrait for T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `()`
-   |
-   = note: this impl is reserved
 
 error: aborting due to previous error
 

diff --git a/tests/ui/traits/solver-cycles/cycle-via-builtin-auto-trait-impl.stderr b/tests/ui/traits/solver-cycles/cycle-via-builtin-auto-trait-impl.stderr
@@ -1,24 +1,12 @@
-error[E0275]: overflow evaluating the requirement `Runtime<RootDatabase>: RefUnwindSafe`
-   |
-   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`cycle_via_builtin_auto_trait_impl`)
-note: required because it appears within the type `RootDatabase`
-  --> $DIR/cycle-via-builtin-auto-trait-impl.rs:13:8
-   |
-LL | struct RootDatabase {
-   |        ^^^^^^^^^^^^
-note: required for `RootDatabase` to implement `Database`
-  --> $DIR/cycle-via-builtin-auto-trait-impl.rs:17:24
+error[E0119]: conflicting implementations of trait `Database` for type `RootDatabase`
+  --> $DIR/cycle-via-builtin-auto-trait-impl.rs:20:1
    |
 LL | impl<T: RefUnwindSafe> Database for T {
-   |         -------------  ^^^^^^^^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-note: required because it appears within the type `Runtime<RootDatabase>`
-  --> $DIR/cycle-via-builtin-auto-trait-impl.rs:24:8
-   |
-LL | struct Runtime<DB: Database> {
-   |        ^^^^^^^
+   | ------------------------------------- first implementation here
+...
+LL | impl Database for RootDatabase {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `RootDatabase`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0275`.
+For more information about this error, try `rustc --explain E0119`.
diff --git a/tests/ui/type-alias-impl-trait/coherence_cross_crate.stderr b/tests/ui/type-alias-impl-trait/coherence_cross_crate.stderr
@@ -5,8 +5,6 @@ LL | impl OtherTrait for Alias {}
    | ------------------------- first implementation here
 LL | impl OtherTrait for i32 {}
    | ^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Alias`
-   |
-   = note: upstream crates may add a new impl of trait `coherence_cross_crate_trait_decl::SomeTrait` for type `i32` in future versions
 
 error: aborting due to previous error