Fix next-solver ICE on PointeeSized goals

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

@@ -2632,6 +2632,8 @@ 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)
+                // `PointeeSized` is removed during lowering.
+                && !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.current.stderr

@@ -0,0 +1,20 @@
+error[E0277]: the trait bound `i32: PointeeSized` is not satisfied
+  --> $DIR/pointee-sized-next-solver-ice.rs:19:21
+   |
+LL |     require_trait::<i32>();
+   |                     ^^^ the trait `PointeeSized` is not implemented for `i32`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/pointee-sized-next-solver-ice.rs:14:1
+   |
+LL | trait PointeeSized {}
+   | ^^^^^^^^^^^^^^^^^^
+note: required by a bound in `require_trait`
+  --> $DIR/pointee-sized-next-solver-ice.rs:16:21
+   |
+LL | fn require_trait<T: PointeeSized>() {}
+   |                     ^^^^^^^^^^^^ required by this bound in `require_trait`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.

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

@@ -0,0 +1,20 @@
+error[E0277]: the trait bound `i32: PointeeSized` is not satisfied
+  --> $DIR/pointee-sized-next-solver-ice.rs:19:21
+   |
+LL |     require_trait::<i32>();
+   |                     ^^^ the trait `PointeeSized` is not implemented for `i32`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/pointee-sized-next-solver-ice.rs:14:1
+   |
+LL | trait PointeeSized {}
+   | ^^^^^^^^^^^^^^^^^^
+note: required by a bound in `require_trait`
+  --> $DIR/pointee-sized-next-solver-ice.rs:16:21
+   |
+LL | fn require_trait<T: PointeeSized>() {}
+   |                     ^^^^^^^^^^^^ required by this bound in `require_trait`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.

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

@@ -0,0 +1,21 @@
+//@ revisions: current next
+//@[next] compile-flags: -Znext-solver
+//@ ignore-compare-mode-next-solver (explicit revisions)
+
+// Regression test for https://github.com/rust-lang/rust/issues/151957
+//
+// When a user-defined trait shares the name `PointeeSized` with
+// `core::marker::PointeeSized`, error reporting tries to check whether
+// the type implements the lang-item `PointeeSized` trait via
+// `predicate_must_hold_modulo_regions`. This creates a `PointeeSized`
+// solver obligation which causes an ICE. We avoid this by skipping the
+// `PointeeSized` lang item during the "similarly named trait" suggestion.
+
+trait PointeeSized {}
+
+fn require_trait<T: PointeeSized>() {}
+
+fn main() {
+    require_trait::<i32>();
+    //~^ ERROR the trait bound `i32: PointeeSized` is not satisfied
+}