revert leak check changes in candidate winnowing

reverts the behavior changes of #119820 to give some
additional time to `sqlx` as it is affected by this change.

Author: lcnr

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -562,7 +562,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         obligation: &PredicateObligation<'tcx>,
     ) -> Result<EvaluationResult, OverflowError> {
         debug_assert!(!self.infcx.next_trait_solver());
-        self.evaluation_probe(|this, _outer_universe| {
+        self.evaluation_probe(|this| {
             let goal =
                 this.infcx.resolve_vars_if_possible((obligation.predicate, obligation.param_env));
             let mut result = this.evaluate_predicate_recursively(
@@ -585,11 +585,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     /// `op`, but this can be overwritten if necessary.
     fn evaluation_probe(
         &mut self,
-        op: impl FnOnce(&mut Self, &mut ty::UniverseIndex) -> Result<EvaluationResult, OverflowError>,
+        op: impl FnOnce(&mut Self) -> Result<EvaluationResult, OverflowError>,
     ) -> Result<EvaluationResult, OverflowError> {
         self.infcx.probe(|snapshot| -> Result<EvaluationResult, OverflowError> {
-            let mut outer_universe = self.infcx.universe();
-            let result = op(self, &mut outer_universe)?;
+            let outer_universe = self.infcx.universe();
+            let result = op(self)?;
 
             match self.infcx.leak_check(outer_universe, Some(snapshot)) {
                 Ok(()) => {}
@@ -1267,9 +1267,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         &mut self,
         stack: &TraitObligationStack<'o, 'tcx>,
         candidate: &SelectionCandidate<'tcx>,
-        leak_check_higher_ranked_goal: LeakCheckHigherRankedGoal,
+        _leak_check_higher_ranked_goal: LeakCheckHigherRankedGoal,
     ) -> Result<EvaluationResult, OverflowError> {
-        let mut result = self.evaluation_probe(|this, outer_universe| {
+        let mut result = self.evaluation_probe(|this| {
             // We eagerly instantiate higher ranked goals to prevent universe errors
             // from impacting candidate selection. This matches the behavior of the new
             // solver. This slightly weakens type inference.
@@ -1280,10 +1280,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // in an overlap error in coherence.
             let p = self.infcx.enter_forall_and_leak_universe(stack.obligation.predicate);
             let obligation = stack.obligation.with(this.tcx(), ty::Binder::dummy(p));
-            match leak_check_higher_ranked_goal {
-                LeakCheckHigherRankedGoal::No => *outer_universe = self.infcx.universe(),
-                LeakCheckHigherRankedGoal::Yes => {}
-            }
 
             match this.confirm_candidate(&obligation, candidate.clone()) {
                 Ok(selection) => {
@@ -1710,13 +1706,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         stack: &TraitObligationStack<'o, 'tcx>,
         where_clause_trait_ref: ty::PolyTraitRef<'tcx>,
     ) -> Result<EvaluationResult, OverflowError> {
-        self.evaluation_probe(|this, outer_universe| {
+        self.evaluation_probe(|this| {
             // Eagerly instantiate higher ranked goals.
             //
             // See the comment in `evaluate_candidate` to see why.
             let p = self.infcx.enter_forall_and_leak_universe(stack.obligation.predicate);
             let obligation = stack.obligation.with(this.tcx(), ty::Binder::dummy(p));
-            *outer_universe = self.infcx.universe();
             match this.match_where_clause_trait_ref(&obligation, where_clause_trait_ref) {
                 Ok(obligations) => this.evaluate_predicates_recursively(stack.list(), obligations),
                 Err(()) => Ok(EvaluatedToErr),

tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-1.rs

@@ -1,3 +1,4 @@
+//@ check-pass
 // cc #119820
 
 trait Trait {}
@@ -21,8 +22,6 @@ where
     // the leak check both candidates may apply and we prefer the
     // `param_env` candidate in winnowing.
     hr_bound::<&T>();
-    //~^ ERROR the parameter type `T` may not live long enough
-    //~| ERROR implementation of `Trait` is not general enough
 }
 
 fn main() {}

tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-1.stderr

@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `for<'a> T: Trait<'a, '_>` is not satisfied
-  --> $DIR/candidate-from-env-universe-err-2.rs:14:5
+  --> $DIR/candidate-from-env-universe-err-2.rs:15:5
    |
 LL |     impl_hr::<T>();
    |     ^^^^^^^^^^^^^^ the trait `for<'a> Trait<'a, '_>` is not implemented for `T`
    |
 note: required by a bound in `impl_hr`
-  --> $DIR/candidate-from-env-universe-err-2.rs:11:19
+  --> $DIR/candidate-from-env-universe-err-2.rs:12:19
    |
 LL | fn impl_hr<'b, T: for<'a> Trait<'a, 'b>>() {}
    |                   ^^^^^^^^^^^^^^^^^^^^^ required by this bound in `impl_hr`

tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-2.current.stderr

@@ -1,5 +1,6 @@
 //@ revisions: current next
 //@[next] compile-flags: -Znext-solver
+//@[current] check-pass
 
 // cc #119820
 
@@ -13,8 +14,6 @@ fn impl_hr<'b, T: for<'a> Trait<'a, 'b>>() {}
 fn not_hr<'a, T: for<'b> Trait<'a, 'b> + OtherTrait<'static>>() {
     impl_hr::<T>();
     //[next]~^ ERROR the trait bound `for<'a> T: Trait<'a, '_>` is not satisfied
-    //[current]~^^ERROR lifetime may not live long enough
-    //[current]~| ERROR implementation of `Trait` is not general enough
 }
 
 fn main() {}

tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-2.next.stderr

@@ -1,23 +1,5 @@
-error: implementation of `Trait` is not general enough
-  --> $DIR/candidate-from-env-universe-err-project.rs:28:5
-   |
-LL |     trait_bound::<T>();
-   |     ^^^^^^^^^^^^^^^^^^ implementation of `Trait` is not general enough
-   |
-   = note: `T` must implement `Trait<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Trait<'static>`
-
-error: implementation of `Trait` is not general enough
-  --> $DIR/candidate-from-env-universe-err-project.rs:39:5
-   |
-LL |     projection_bound::<T>();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Trait` is not general enough
-   |
-   = note: `T` must implement `Trait<'0>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Trait<'static>`
-
 error[E0308]: mismatched types
-  --> $DIR/candidate-from-env-universe-err-project.rs:39:5
+  --> $DIR/candidate-from-env-universe-err-project.rs:38:5
    |
 LL |     projection_bound::<T>();
    |     ^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
@@ -31,7 +13,7 @@ LL | fn projection_bound<T: for<'a> Trait<'a, Assoc = usize>>() {}
    |                                          ^^^^^^^^^^^^^
 
 error[E0308]: mismatched types
-  --> $DIR/candidate-from-env-universe-err-project.rs:55:30
+  --> $DIR/candidate-from-env-universe-err-project.rs:53:30
    |
 LL |     let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
@@ -40,7 +22,7 @@ LL |     let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
               found associated type `<T as Trait<'a>>::Assoc`
 
 error[E0308]: mismatched types
-  --> $DIR/candidate-from-env-universe-err-project.rs:55:30
+  --> $DIR/candidate-from-env-universe-err-project.rs:53:30
    |
 LL |     let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
@@ -49,6 +31,6 @@ LL |     let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
               found associated type `<T as Trait<'a>>::Assoc`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: aborting due to 5 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0308`.

tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-2.rs

@@ -15,7 +15,7 @@ LL | fn function1<T: Trait<'static> + for<'a> Trait<'a>>() {
    |                                +++++++++++++++++++
 
 error[E0277]: the trait bound `for<'a> T: Trait<'a>` is not satisfied
-  --> $DIR/candidate-from-env-universe-err-project.rs:39:24
+  --> $DIR/candidate-from-env-universe-err-project.rs:38:24
    |
 LL |     projection_bound::<T>();
    |                        ^ the trait `for<'a> Trait<'a>` is not implemented for `T`
@@ -31,7 +31,7 @@ LL | fn function2<T: Trait<'static, Assoc = usize> + for<'a> Trait<'a>>() {
    |                                               +++++++++++++++++++
 
 error[E0271]: type mismatch resolving `<T as Trait<'a>>::Assoc == usize`
-  --> $DIR/candidate-from-env-universe-err-project.rs:39:24
+  --> $DIR/candidate-from-env-universe-err-project.rs:38:24
    |
 LL |     projection_bound::<T>();
    |                        ^ type mismatch resolving `<T as Trait<'a>>::Assoc == usize`
@@ -48,13 +48,13 @@ LL | fn projection_bound<T: for<'a> Trait<'a, Assoc = usize>>() {}
    |                                          ^^^^^^^^^^^^^ required by this bound in `projection_bound`
 
 error: higher-ranked subtype error
-  --> $DIR/candidate-from-env-universe-err-project.rs:55:30
+  --> $DIR/candidate-from-env-universe-err-project.rs:53:30
    |
 LL |     let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: higher-ranked subtype error
-  --> $DIR/candidate-from-env-universe-err-project.rs:55:30
+  --> $DIR/candidate-from-env-universe-err-project.rs:53:30
    |
 LL |     let _higher_ranked_norm: for<'a> fn(<T as Trait<'a>>::Assoc) = |_| ();
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-project.current.stderr

@@ -27,7 +27,6 @@ fn function1<T: Trait<'static>>() {
     // We prefer env candidates over impl candidatescausing this to succeed.
     trait_bound::<T>();
     //[next]~^ ERROR the trait bound `for<'a> T: Trait<'a>` is not satisfied
-    //[current]~^^ ERROR implementation of `Trait` is not general enough
 }
 
 fn function2<T: Trait<'static, Assoc = usize>>() {
@@ -39,8 +38,7 @@ fn function2<T: Trait<'static, Assoc = usize>>() {
     projection_bound::<T>();
     //[next]~^ ERROR type mismatch resolving `<T as Trait<'a>>::Assoc == usize`
     //[next]~| ERROR the trait bound `for<'a> T: Trait<'a>` is not satisfied
-    //[current]~^^^ ERROR implementation of `Trait` is not general enough
-    //[current]~| ERROR mismatched types
+    //[current]~^^^ ERROR mismatched types
 }
 
 fn function3<T: Trait<'static, Assoc = usize>>() {

tests/ui/higher-ranked/leak-check/candidate-from-env-universe-err-project.next.stderr

@@ -1,19 +1,19 @@
 error[E0283]: type annotations needed
-  --> $DIR/leak-check-in-selection-2.rs:16:5
+  --> $DIR/leak-check-in-selection-2.rs:17:5
    |
 LL |     impls_trait::<(), _>();
    |     ^^^^^^^^^^^^^^^^^^^^ cannot infer type of the type parameter `U` declared on the function `impls_trait`
    |
 note: multiple `impl`s satisfying `for<'a> (): Trait<&'a str, _>` found
-  --> $DIR/leak-check-in-selection-2.rs:9:1
+  --> $DIR/leak-check-in-selection-2.rs:10:1
    |
 LL | impl<'a> Trait<&'a str, &'a str> for () {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | impl<'a> Trait<&'a str, String> for () {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 note: required by a bound in `impls_trait`
-  --> $DIR/leak-check-in-selection-2.rs:13:19
+  --> $DIR/leak-check-in-selection-2.rs:14:19
    |
 LL | fn impls_trait<T: for<'a> Trait<&'a str, U>, U>() {}
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `impls_trait`