Bubble the opaque type ordering int opaque type handling

Author: oli-obk

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -103,7 +103,7 @@ impl<'tcx> InferCtxt<'tcx> {
             return Ok(InferOk { value: (), obligations: vec![] });
         }
         let (a, b) = if a_is_expected { (a, b) } else { (b, a) };
-        let process = |a: Ty<'tcx>, b: Ty<'tcx>| match *a.kind() {
+        let process = |a: Ty<'tcx>, b: Ty<'tcx>, a_is_expected| match *a.kind() {
             ty::Opaque(def_id, substs) if def_id.is_local() => {
                 let def_id = def_id.expect_local();
                 let origin = match self.defining_use_anchor {
@@ -169,13 +169,14 @@ impl<'tcx> InferCtxt<'tcx> {
                     param_env,
                     b,
                     origin,
+                    a_is_expected,
                 ))
             }
             _ => None,
         };
-        if let Some(res) = process(a, b) {
+        if let Some(res) = process(a, b, true) {
             res
-        } else if let Some(res) = process(b, a) {
+        } else if let Some(res) = process(b, a, false) {
             res
         } else {
             let (a, b) = self.resolve_vars_if_possible((a, b));
@@ -514,13 +515,14 @@ impl UseKind {
 
 impl<'tcx> InferCtxt<'tcx> {
     #[instrument(skip(self), level = "debug")]
-    pub fn register_hidden_type(
+    fn register_hidden_type(
         &self,
         opaque_type_key: OpaqueTypeKey<'tcx>,
         cause: ObligationCause<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         hidden_ty: Ty<'tcx>,
         origin: hir::OpaqueTyOrigin,
+        a_is_expected: bool,
     ) -> InferResult<'tcx, ()> {
         let tcx = self.tcx;
         let OpaqueTypeKey { def_id, substs } = opaque_type_key;
@@ -539,7 +541,8 @@ impl<'tcx> InferCtxt<'tcx> {
             origin,
         );
         if let Some(prev) = prev {
-            obligations = self.at(&cause, param_env).eq(prev, hidden_ty)?.obligations;
+            obligations =
+                self.at(&cause, param_env).eq_exp(a_is_expected, prev, hidden_ty)?.obligations;
         }
 
         let item_bounds = tcx.bound_explicit_item_bounds(def_id.to_def_id());