1 files changed, 34 insertions, 0 deletions
diff --git a/compiler/rustc_traits/src/evaluate_obligation.rs b/compiler/rustc_traits/src/evaluate_obligation.rs
new file mode 100644
index 000000000..49c9ba459
--- /dev/null
+++ b/compiler/rustc_traits/src/evaluate_obligation.rs
@@ -0,0 +1,34 @@
+use rustc_infer::infer::{DefiningAnchor, TyCtxtInferExt};
+use rustc_middle::ty::query::Providers;
+use rustc_middle::ty::{ParamEnvAnd, TyCtxt};
+use rustc_span::source_map::DUMMY_SP;
+use rustc_trait_selection::traits::query::CanonicalPredicateGoal;
+use rustc_trait_selection::traits::{
+    EvaluationResult, Obligation, ObligationCause, OverflowError, SelectionContext, TraitQueryMode,
+};
+
+pub(crate) fn provide(p: &mut Providers) {
+    *p = Providers { evaluate_obligation, ..*p };
+}
+
+fn evaluate_obligation<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    canonical_goal: CanonicalPredicateGoal<'tcx>,
+) -> Result<EvaluationResult, OverflowError> {
+    debug!("evaluate_obligation(canonical_goal={:#?})", canonical_goal);
+    // HACK This bubble is required for this tests to pass:
+    // impl-trait/issue99642.rs
+    tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::Bubble).enter_with_canonical(
+        DUMMY_SP,
+        &canonical_goal,
+        |ref infcx, goal, _canonical_inference_vars| {
+            debug!("evaluate_obligation: goal={:#?}", goal);
+            let ParamEnvAnd { param_env, value: predicate } = goal;
+
+            let mut selcx = SelectionContext::with_query_mode(&infcx, TraitQueryMode::Canonical);
+            let obligation = Obligation::new(ObligationCause::dummy(), param_env, predicate);
+
+            selcx.evaluate_root_obligation(&obligation)
+        },
+    )
+}