Report overflows gracefully with new solver

3 files changed, 9 insertions, 4 deletions

diff --git a/compiler/rustc_infer/src/traits/engine.rs b/compiler/rustc_infer/src/traits/engine.rs
index f75344f20b6..2f0a19b46de 100644
--- a/compiler/rustc_infer/src/traits/engine.rs
+++ b/compiler/rustc_infer/src/traits/engine.rs
@@ -38,7 +38,7 @@ pub trait TraitEngine<'tcx>: 'tcx {
 
     fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
 
-    fn collect_remaining_errors(&mut self) -> Vec<FulfillmentError<'tcx>>;
+    fn collect_remaining_errors(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
 
     fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>;
 
@@ -78,6 +78,6 @@ impl<'tcx, T: ?Sized + TraitEngine<'tcx>> TraitEngineExt<'tcx> for T {
             return errors;
         }
 
-        self.collect_remaining_errors()
+        self.collect_remaining_errors(infcx)
     }
 }
diff --git a/compiler/rustc_infer/src/traits/mod.rs b/compiler/rustc_infer/src/traits/mod.rs
index dd9b2e548c7..e01b6caf430 100644
--- a/compiler/rustc_infer/src/traits/mod.rs
+++ b/compiler/rustc_infer/src/traits/mod.rs
@@ -128,7 +128,11 @@ pub enum FulfillmentErrorCode<'tcx> {
     CodeProjectionError(MismatchedProjectionTypes<'tcx>),
     CodeSubtypeError(ExpectedFound<Ty<'tcx>>, TypeError<'tcx>), // always comes from a SubtypePredicate
     CodeConstEquateError(ExpectedFound<Const<'tcx>>, TypeError<'tcx>),
-    CodeAmbiguity,
+    CodeAmbiguity {
+        /// Overflow reported from the new solver `-Ztrait-solver=next`, which will
+        /// be reported as an regular error as opposed to a fatal error.
+        overflow: bool,
+    },
 }
 
 impl<'tcx, O> Obligation<'tcx, O> {
diff --git a/compiler/rustc_infer/src/traits/structural_impls.rs b/compiler/rustc_infer/src/traits/structural_impls.rs
index 3a5273b0359..1563d92af0e 100644
--- a/compiler/rustc_infer/src/traits/structural_impls.rs
+++ b/compiler/rustc_infer/src/traits/structural_impls.rs
@@ -46,7 +46,8 @@ impl<'tcx> fmt::Debug for traits::FulfillmentErrorCode<'tcx> {
             super::CodeConstEquateError(ref a, ref b) => {
                 write!(f, "CodeConstEquateError({:?}, {:?})", a, b)
             }
-            super::CodeAmbiguity => write!(f, "Ambiguity"),
+            super::CodeAmbiguity { overflow: false } => write!(f, "Ambiguity"),
+            super::CodeAmbiguity { overflow: true } => write!(f, "Overflow"),
             super::CodeCycle(ref cycle) => write!(f, "Cycle({:?})", cycle),
         }
     }