Add tcx::lower_impl_trait_in_trait_to_assoc_ty to avoid accessing through sess.opts.unstable_opts

Author: spastorino

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1104,7 +1104,7 @@ fn should_encode_const(def_kind: DefKind) -> bool {
 // We only encode impl trait in trait when using `lower-impl-trait-in-trait-to-assoc-ty` unstable
 // option.
 fn should_encode_fn_impl_trait_in_trait<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
-    if tcx.sess.opts.unstable_opts.lower_impl_trait_in_trait_to_assoc_ty
+    if tcx.lower_impl_trait_in_trait_to_assoc_ty()
         && let Some(assoc_item) = tcx.opt_associated_item(def_id)
         && assoc_item.container == ty::AssocItemContainer::TraitContainer
         && assoc_item.kind == ty::AssocKind::Fn

compiler/rustc_middle/src/ty/context.rs

@@ -2439,6 +2439,10 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn trait_solver_next(self) -> bool {
         self.sess.opts.unstable_opts.trait_solver == rustc_session::config::TraitSolver::Next
     }
+
+    pub fn lower_impl_trait_in_trait_to_assoc_ty(self) -> bool {
+        self.sess.opts.unstable_opts.lower_impl_trait_in_trait_to_assoc_ty
+    }
 }
 
 impl<'tcx> TyCtxtAt<'tcx> {

compiler/rustc_ty_utils/src/assoc.rs

@@ -23,7 +23,7 @@ fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
     let item = tcx.hir().expect_item(def_id.expect_local());
     match item.kind {
         hir::ItemKind::Trait(.., ref trait_item_refs) => {
-            if tcx.sess.opts.unstable_opts.lower_impl_trait_in_trait_to_assoc_ty {
+            if tcx.lower_impl_trait_in_trait_to_assoc_ty() {
                 // We collect RPITITs for each trait method's return type and create a
                 // corresponding associated item using associated_items_for_impl_trait_in_trait
                 // query.
@@ -54,7 +54,7 @@ fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
             }
         }
         hir::ItemKind::Impl(ref impl_) => {
-            if tcx.sess.opts.unstable_opts.lower_impl_trait_in_trait_to_assoc_ty {
+            if tcx.lower_impl_trait_in_trait_to_assoc_ty() {
                 // We collect RPITITs for each trait method's return type, on the impl side too and
                 // create a corresponding associated item using
                 // associated_items_for_impl_trait_in_trait query.