X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=compiler%2Frustc_infer%2Fsrc%2Ftraits%2Fengine.rs;h=f75344f20b6d98e842f622dfd3e39d23e8e22385;hb=a67649675014546ce454d65bc8fe3ebd18e6a319;hp=fcde00056cbf1c4cf4738e80e851497506a05dcf;hpb=82455a799ec408798811d951b9ceb45bdfe57753;p=rust.git

diff --git a/compiler/rustc_infer/src/traits/engine.rs b/compiler/rustc_infer/src/traits/engine.rs
index fcde00056cb..f75344f20b6 100644
--- a/compiler/rustc_infer/src/traits/engine.rs
+++ b/compiler/rustc_infer/src/traits/engine.rs
@@ -36,11 +36,19 @@ fn register_predicate_obligation(
         obligation: PredicateObligation<'tcx>,
     );
 
-    fn select_all_or_error(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
-
     fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
 
+    fn collect_remaining_errors(&mut self) -> Vec<FulfillmentError<'tcx>>;
+
     fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>;
+
+    /// Among all pending obligations, collect those are stalled on a inference variable which has
+    /// changed since the last call to `select_where_possible`. Those obligations are marked as
+    /// successful and returned.
+    fn drain_unstalled_obligations(
+        &mut self,
+        infcx: &InferCtxt<'tcx>,
+    ) -> Vec<PredicateObligation<'tcx>>;
 }
 
 pub trait TraitEngineExt<'tcx> {
@@ -49,6 +57,8 @@ fn register_predicate_obligations(
         infcx: &InferCtxt<'tcx>,
         obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
     );
+
+    fn select_all_or_error(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
 }
 
 impl<'tcx, T: ?Sized + TraitEngine<'tcx>> TraitEngineExt<'tcx> for T {
@@ -61,4 +71,13 @@ fn register_predicate_obligations(
             self.register_predicate_obligation(infcx, obligation);
         }
     }
+
+    fn select_all_or_error(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>> {
+        let errors = self.select_where_possible(infcx);
+        if !errors.is_empty() {
+            return errors;
+        }
+
+        self.collect_remaining_errors()
+    }
 }