From 5775190dbacd8334e6b146180c9268a33be15a25 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Mon, 30 Dec 2024 18:48:53 +0000
Subject: [PATCH] Make sure to scrape region constraints from deeply
 normalizing type outlives assumptions in borrowck

---
 .../src/type_check/free_region_relations.rs   | 67 +++++++++++++------
 .../known-type-outlives-has-constraints.rs    | 13 ++++
 2 files changed, 61 insertions(+), 19 deletions(-)
 create mode 100644 tests/ui/traits/next-solver/known-type-outlives-has-constraints.rs

diff --git a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
index ea965eb654583..edf612f4e97a4 100644
--- a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
+++ b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
@@ -5,13 +5,14 @@ use rustc_infer::infer::canonical::QueryRegionConstraints;
 use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::region_constraints::GenericKind;
 use rustc_infer::infer::{InferCtxt, outlives};
+use rustc_infer::traits::ScrubbedTraitError;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::traits::query::OutlivesBound;
 use rustc_middle::ty::{self, RegionVid, Ty, TypeVisitableExt};
 use rustc_span::{ErrorGuaranteed, Span};
-use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
-use rustc_trait_selection::solve::deeply_normalize;
+use rustc_trait_selection::solve::NoSolution;
+use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
 use rustc_trait_selection::traits::query::type_op::{self, TypeOp};
 use tracing::{debug, instrument};
 use type_op::TypeOpOutput;
@@ -229,24 +230,14 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         let mut constraints = vec![];
         let mut known_type_outlives_obligations = vec![];
         for bound in param_env.caller_bounds() {
-            let Some(mut outlives) = bound.as_type_outlives_clause() else { continue };
-
-            // In the new solver, normalize the type-outlives obligation assumptions.
-            if self.infcx.next_trait_solver() {
-                match deeply_normalize(
-                    self.infcx.at(&ObligationCause::misc(span, defining_ty_def_id), param_env),
+            if let Some(outlives) = bound.as_type_outlives_clause() {
+                self.normalize_and_push_type_outlives_obligation(
                     outlives,
-                ) {
-                    Ok(normalized_outlives) => {
-                        outlives = normalized_outlives;
-                    }
-                    Err(e) => {
-                        self.infcx.err_ctxt().report_fulfillment_errors(e);
-                    }
-                }
-            }
-
-            known_type_outlives_obligations.push(outlives);
+                    span,
+                    &mut known_type_outlives_obligations,
+                    &mut constraints,
+                );
+            };
         }
 
         let unnormalized_input_output_tys = self
@@ -356,6 +347,44 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         }
     }
 
+    fn normalize_and_push_type_outlives_obligation(
+        &self,
+        mut outlives: ty::PolyTypeOutlivesPredicate<'tcx>,
+        span: Span,
+        known_type_outlives_obligations: &mut Vec<ty::PolyTypeOutlivesPredicate<'tcx>>,
+        constraints: &mut Vec<&QueryRegionConstraints<'tcx>>,
+    ) {
+        // In the new solver, normalize the type-outlives obligation assumptions.
+        if self.infcx.next_trait_solver() {
+            let Ok(TypeOpOutput {
+                output: normalized_outlives,
+                constraints: constraints_normalize,
+                error_info: _,
+            }) = CustomTypeOp::new(
+                |ocx| {
+                    ocx.deeply_normalize(
+                        &ObligationCause::dummy_with_span(span),
+                        self.param_env,
+                        outlives,
+                    )
+                    .map_err(|_: Vec<ScrubbedTraitError<'tcx>>| NoSolution)
+                },
+                "normalize type outlives obligation",
+            )
+            .fully_perform(self.infcx, span)
+            else {
+                self.infcx.dcx().delayed_bug(format!("could not normalize {outlives:?}"));
+                return;
+            };
+            outlives = normalized_outlives;
+            if let Some(c) = constraints_normalize {
+                constraints.push(c);
+            }
+        }
+
+        known_type_outlives_obligations.push(outlives);
+    }
+
     /// Update the type of a single local, which should represent
     /// either the return type of the MIR or one of its arguments. At
     /// the same time, compute and add any implied bounds that come
diff --git a/tests/ui/traits/next-solver/known-type-outlives-has-constraints.rs b/tests/ui/traits/next-solver/known-type-outlives-has-constraints.rs
new file mode 100644
index 0000000000000..55fea005ea1ab
--- /dev/null
+++ b/tests/ui/traits/next-solver/known-type-outlives-has-constraints.rs
@@ -0,0 +1,13 @@
+//@ compile-flags: -Znext-solver
+//@ check-pass
+
+trait Norm {
+    type Out;
+}
+impl<'a, T: 'a> Norm for &'a T {
+    type Out = T;
+}
+
+fn hello<'a, T: 'a>() where <&'a T as Norm>::Out: 'a {}
+
+fn main() {}