add eq to InferCtxtExt

compiler/rustc_trait_selection/src/solve/infcx_ext.rs

@@ -1,11 +1,28 @@
+use rustc_infer::infer::at::ToTrace;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc_infer::infer::InferCtxt;
-use rustc_middle::ty::Ty;
+use rustc_infer::infer::{InferCtxt, InferOk};
+use rustc_infer::traits::query::NoSolution;
+use rustc_infer::traits::ObligationCause;
+use rustc_middle::ty::{self, Ty};
 use rustc_span::DUMMY_SP;
 
+use super::Goal;
+
 /// Methods used inside of the canonical queries of the solver.
+///
+/// Most notably these do not care about diagnostics information.
+/// If you find this while looking for methods to use outside of the
+/// solver, you may look at the implementation of these method for
+/// help.
 pub(super) trait InferCtxtExt<'tcx> {
     fn next_ty_infer(&self) -> Ty<'tcx>;
+
+    fn eq<T: ToTrace<'tcx>>(
+        &self,
+        param_env: ty::ParamEnv<'tcx>,
+        lhs: T,
+        rhs: T,
+    ) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution>;
 }
 
 impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
@@ -15,4 +32,23 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
             span: DUMMY_SP,
         })
     }
+
+    #[instrument(level = "debug", skip(self, param_env), ret)]
+    fn eq<T: ToTrace<'tcx>>(
+        &self,
+        param_env: ty::ParamEnv<'tcx>,
+        lhs: T,
+        rhs: T,
+    ) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution> {
+        self.at(&ObligationCause::dummy(), param_env)
+            .define_opaque_types(false)
+            .eq(lhs, rhs)
+            .map(|InferOk { value: (), obligations }| {
+                obligations.into_iter().map(|o| o.into()).collect()
+            })
+            .map_err(|e| {
+                debug!(?e, "failed to equate");
+                NoSolution
+            })
+    }
 }