Deeply normalize when computing implied outlives bounds

Author: compiler-errors

Diff for: compiler/rustc_trait_selection/src/traits/normalize.rs

@@ -66,7 +66,7 @@ impl<'tcx> At<'_, 'tcx> {
             let value = self
                 .normalize(value)
                 .into_value_registering_obligations(self.infcx, &mut *fulfill_cx);
-            let errors = fulfill_cx.select_where_possible(self.infcx);
+            let errors = fulfill_cx.select_all_or_error(self.infcx);
             let value = self.infcx.resolve_vars_if_possible(value);
             if errors.is_empty() { Ok(value) } else { Err(errors) }
         }

Diff for: compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs

@@ -59,12 +59,13 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
     param_env: ty::ParamEnv<'tcx>,
     ty: Ty<'tcx>,
 ) -> Result<Vec<OutlivesBound<'tcx>>, NoSolution> {
-    let normalize_op = |ty| {
-        let ty = ocx.normalize(&ObligationCause::dummy(), param_env, ty);
+    let normalize_op = |ty| -> Result<_, NoSolution> {
+        let ty = ocx
+            .deeply_normalize(&ObligationCause::dummy(), param_env, ty)
+            .map_err(|_| NoSolution)?;
         if !ocx.select_all_or_error().is_empty() {
             return Err(NoSolution);
         }
-        let ty = ocx.infcx.resolve_vars_if_possible(ty);
         let ty = OpportunisticRegionResolver::new(&ocx.infcx).fold_ty(ty);
         Ok(ty)
     };

Diff for: tests/ui/traits/next-solver/normalize-in-implied_outlives_bounds.rs

@@ -0,0 +1,46 @@
+//@ check-pass
+//@ compile-flags: -Znext-solver
+
+// Minimized example from `rustc_type_ir` that demonstrates a missing deep normalization
+// in the new solver when computing the implies outlives bounds of an impl.
+
+use std::marker::PhantomData;
+use std::ops::Deref;
+
+pub struct SearchGraph<D: Delegate, X = <D as Delegate>::Cx> {
+    d: PhantomData<D>,
+    x: PhantomData<X>,
+}
+
+pub trait Delegate {
+    type Cx;
+}
+
+struct SearchGraphDelegate<D: SolverDelegate> {
+    _marker: PhantomData<D>,
+}
+
+impl<D> Delegate for SearchGraphDelegate<D>
+where
+    D: SolverDelegate,
+{
+    type Cx = D::Interner;
+}
+
+pub trait SolverDelegate {
+    type Interner;
+}
+
+struct EvalCtxt<'a, D, I>
+where
+    D: SolverDelegate<Interner = I>,
+{
+    search_graph: &'a SearchGraph<SearchGraphDelegate<D>>,
+}
+
+impl<'a, D, I> EvalCtxt<'a, D, <D as SolverDelegate>::Interner>
+where
+    D: SolverDelegate<Interner = I>
+{}
+
+fn main() {}