Encode opt_rpitit_info for associated types

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1087,6 +1087,8 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             _ => bug!("cannot get associated-item of `{:?}`", self.def_key(id)),
         };
         let container = self.root.tables.assoc_container.get(self, id).unwrap();
+        let opt_rpitit_info =
+            self.root.tables.opt_rpitit_info.get(self, id).map(|d| d.decode(self));
 
         ty::AssocItem {
             name,
@@ -1095,8 +1097,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             trait_item_def_id: self.get_trait_item_def_id(id),
             container,
             fn_has_self_parameter: has_self,
-            // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): We need to encode this
-            opt_rpitit_info: None,
+            opt_rpitit_info,
         }
     }
 

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1350,6 +1350,10 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         if trait_item.kind == ty::AssocKind::Fn {
             record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
         }
+        if let Some(rpitit_info) = trait_item.opt_rpitit_info {
+            let rpitit_info = self.lazy(rpitit_info);
+            self.tables.opt_rpitit_info.set_some(def_id.index, rpitit_info);
+        }
     }
 
     fn encode_info_for_impl_item(&mut self, def_id: DefId) {
@@ -1383,6 +1387,10 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
             self.tables.is_intrinsic.set(def_id.index, tcx.is_intrinsic(def_id));
         }
+        if let Some(rpitit_info) = impl_item.opt_rpitit_info {
+            let rpitit_info = self.lazy(rpitit_info);
+            self.tables.opt_rpitit_info.set_some(def_id.index, rpitit_info);
+        }
     }
 
     fn encode_mir(&mut self) {

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -355,6 +355,7 @@ define_tables! {
     inferred_outlives_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
     inherent_impls: Table<DefIndex, LazyArray<DefIndex>>,
     associated_items_for_impl_trait_in_trait: Table<DefIndex, LazyArray<DefId>>,
+    opt_rpitit_info: Table<DefIndex, Option<LazyValue<ty::ImplTraitInTraitData>>>,
 
 - optional:
     attributes: Table<DefIndex, LazyArray<ast::Attribute>>,

compiler/rustc_middle/src/ty/parameterized.rs

@@ -63,6 +63,7 @@ trivially_parameterized_over_tcx! {
     ty::DeducedParamAttrs,
     ty::Generics,
     ty::ImplPolarity,
+    ty::ImplTraitInTraitData,
     ty::ReprOptions,
     ty::TraitDef,
     ty::UnusedGenericParams,

compiler/rustc_ty_utils/src/ty.rs

@@ -119,12 +119,9 @@ fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
 fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
     // When computing the param_env of an RPITIT, copy param_env of the containing function. The
     // synthesized associated type doesn't have extra predicates to assume.
-    let def_id =
-        if let Some(ImplTraitInTraitData::Trait { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id) {
-            fn_def_id
-        } else {
-            def_id
-        };
+    if let Some(ImplTraitInTraitData::Trait { fn_def_id, .. }) = tcx.opt_rpitit_info(def_id) {
+        return tcx.param_env(fn_def_id);
+    }
 
     // Compute the bounds on Self and the type parameters.
     let ty::InstantiatedPredicates { mut predicates, .. } =