Extract obligation resolution to function

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -17,7 +17,7 @@ use crate::traits::{
 use rustc_errors::Diagnostic;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_hir::CRATE_HIR_ID;
-use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::{util, TraitEngine};
 use rustc_middle::traits::specialization_graph::OverlapMode;
 use rustc_middle::ty::fast_reject::{self, TreatParams};
@@ -361,11 +361,29 @@ fn negative_impl_exists<'cx, 'tcx>(
     o: &PredicateObligation<'tcx>,
 ) -> bool {
     let infcx = &selcx.infcx().fork();
+
+    if resolve_negative_obligation(infcx, param_env, region_context, o) {
+        return true;
+    }
+
+    for o in util::elaborate_predicates(infcx.tcx, iter::once(o.predicate)) {
+        if resolve_negative_obligation(infcx, param_env, region_context, &o) {
+            return true;
+        }
+    }
+
+    false
+}
+
+#[instrument(level = "debug", skip(infcx))]
+fn resolve_negative_obligation<'cx, 'tcx>(
+    infcx: &InferCtxt<'cx, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    region_context: DefId,
+    o: &PredicateObligation<'tcx>,
+) -> bool {
     let tcx = infcx.tcx;
 
-    let super_obligations = util::elaborate_predicates(tcx, iter::once(o.predicate));
-
-    for o in iter::once(o.clone()).chain(super_obligations) {
     if let Some(o) = o.flip_polarity(tcx) {
         let mut fulfillment_cx = FulfillmentContext::new();
         fulfillment_cx.register_predicate_obligation(infcx, o);
@@ -373,7 +391,7 @@ fn negative_impl_exists<'cx, 'tcx>(
         let errors = fulfillment_cx.select_all_or_error(infcx);
 
         if !errors.is_empty() {
-                continue;
+            return false;
         }
 
         let mut outlives_env = OutlivesEnvironment::new(param_env);
@@ -392,16 +410,14 @@ fn negative_impl_exists<'cx, 'tcx>(
             param_env,
         );
 
-            let errors =
-                infcx.resolve_regions(region_context, &outlives_env, RegionckMode::default());
+        let errors = infcx.resolve_regions(region_context, &outlives_env, RegionckMode::default());
 
         if !errors.is_empty() {
-                continue;
+            return false;
         }
 
         return true;
     }
-    }
 
     false
 }