Fix next-solver ICE on PointeeSized goals

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -2596,6 +2596,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             trait_def_id != *def_id
                 && trait_name == self.tcx.item_name(def_id)
                 && trait_has_same_params(*def_id)
+                // Skip `PointeeSized` here to avoid creating `PointeeSized` solver obligations during error reporting.
+                && !self.tcx.is_lang_item(*def_id, LangItem::PointeeSized)
                 && self.predicate_must_hold_modulo_regions(&Obligation::new(
                     self.tcx,
                     obligation.cause.clone(),

tests/ui/cycle-trait/pointee-sized-next-solver-ice.rs

@@ -0,0 +1,20 @@
+//@ compile-flags: -Znext-solver=globally
+
+// Regression test for #151957
+
+trait PointeeSized {
+    type Undefined;
+}
+
+struct T;
+
+impl PointeeSized for T
+//~^ ERROR not all trait items implemented, missing: `Undefined`
+//~| ERROR the trait bound `T: PointeeSized` is not satisfied
+where
+    <T as PointeeSized>::Undefined: PointeeSized,
+//~^ ERROR the trait bound `T: PointeeSized` is not satisfied
+//~| ERROR the trait bound `T: PointeeSized` is not satisfied
+{}
+
+fn main() {}

tests/ui/cycle-trait/pointee-sized-next-solver-ice.stderr

@@ -0,0 +1,92 @@
+error[E0046]: not all trait items implemented, missing: `Undefined`
+  --> $DIR/pointee-sized-next-solver-ice.rs:11:1
+   |
+LL |       type Undefined;
+   |       -------------- `Undefined` from trait
+...
+LL | / impl PointeeSized for T
+LL | |
+LL | |
+LL | | where
+LL | |     <T as PointeeSized>::Undefined: PointeeSized,
+   | |_________________________________________________^ missing `Undefined` in implementation
+
+error[E0277]: the trait bound `T: PointeeSized` is not satisfied
+  --> $DIR/pointee-sized-next-solver-ice.rs:15:5
+   |
+LL |     <T as PointeeSized>::Undefined: PointeeSized,
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
+   |
+help: the trait `PointeeSized` is not implemented for `T`
+  --> $DIR/pointee-sized-next-solver-ice.rs:9:1
+   |
+LL | struct T;
+   | ^^^^^^^^
+help: the trait `PointeeSized` is implemented for `T`
+  --> $DIR/pointee-sized-next-solver-ice.rs:11:1
+   |
+LL | / impl PointeeSized for T
+LL | |
+LL | |
+LL | | where
+LL | |     <T as PointeeSized>::Undefined: PointeeSized,
+   | |_________________________________________________^
+   = help: see issue #48214
+help: add `#![feature(trivial_bounds)]` to the crate attributes to enable
+   |
+LL + #![feature(trivial_bounds)]
+   |
+
+error[E0277]: the trait bound `T: PointeeSized` is not satisfied
+  --> $DIR/pointee-sized-next-solver-ice.rs:11:23
+   |
+LL | impl PointeeSized for T
+   |                       ^ unsatisfied trait bound
+   |
+help: the trait `PointeeSized` is not implemented for `T`
+  --> $DIR/pointee-sized-next-solver-ice.rs:9:1
+   |
+LL | struct T;
+   | ^^^^^^^^
+help: the trait `PointeeSized` is implemented for `T`
+  --> $DIR/pointee-sized-next-solver-ice.rs:11:1
+   |
+LL | / impl PointeeSized for T
+LL | |
+LL | |
+LL | | where
+LL | |     <T as PointeeSized>::Undefined: PointeeSized,
+   | |_________________________________________________^
+
+error[E0277]: the trait bound `T: PointeeSized` is not satisfied
+  --> $DIR/pointee-sized-next-solver-ice.rs:15:37
+   |
+LL |     <T as PointeeSized>::Undefined: PointeeSized,
+   |                                     ^^^^^^^^^^^^ unsatisfied trait bound
+   |
+help: the trait `PointeeSized` is not implemented for `T`
+  --> $DIR/pointee-sized-next-solver-ice.rs:9:1
+   |
+LL | struct T;
+   | ^^^^^^^^
+help: the trait `PointeeSized` is implemented for `T`
+  --> $DIR/pointee-sized-next-solver-ice.rs:11:1
+   |
+LL | / impl PointeeSized for T
+LL | |
+LL | |
+LL | | where
+LL | |     <T as PointeeSized>::Undefined: PointeeSized,
+   | |_________________________________________________^
+note: required by a bound in `PointeeSized`
+  --> $DIR/pointee-sized-next-solver-ice.rs:5:1
+   |
+LL | / trait PointeeSized {
+LL | |     type Undefined;
+LL | | }
+   | |_^ required by this bound in `PointeeSized`
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0046, E0277.
+For more information about an error, try `rustc --explain E0046`.