ty::Alias review comments

Author: WaffleLapkin

compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs

@@ -54,7 +54,6 @@ use rustc_abi::ExternAbi;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::{Applicability, Diag, DiagStyledString, IntoDiagArg, StringPart, pluralize};
 use rustc_hir as hir;
-use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::lang_items::LangItem;
@@ -182,11 +181,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
     pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
         let (def_id, args) = match *ty.kind() {
-            ty::Alias(ty::AliasTy { kind, args, .. })
-                if self.tcx.def_kind(kind.def_id()) == DefKind::OpaqueTy =>
-            {
-                (kind.def_id(), args)
-            }
+            ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id }, args, .. }) => (def_id, args),
             ty::Alias(ty::AliasTy { kind, args, .. })
                 if self.tcx.is_impl_trait_in_trait(kind.def_id()) =>
             {

compiler/rustc_type_ir/src/interner.rs

@@ -196,6 +196,7 @@ pub trait Interner:
     type VariancesOf: Copy + Debug + SliceLike<Item = ty::Variance>;
     fn variances_of(self, def_id: Self::DefId) -> Self::VariancesOf;
 
+    // FIXME: remove `def_id` param after `AliasTermKind` contains `def_id` within
     fn opt_alias_variances(
         self,
         kind: impl Into<ty::AliasTermKind>,

compiler/rustc_type_ir/src/predicate.rs

@@ -644,52 +644,26 @@ impl<I: Interner> AliasTerm<I> {
     }
 
     pub fn to_term(self, interner: I) -> I::Term {
-        match self.kind(interner) {
-            AliasTermKind::ProjectionTy => Ty::new_alias(
-                interner,
-                ty::AliasTy {
-                    kind: ty::AliasTyKind::Projection { def_id: self.def_id },
-                    args: self.args,
-                    _use_alias_ty_new_instead: (),
-                },
-            )
-            .into(),
-            AliasTermKind::InherentTy => Ty::new_alias(
-                interner,
-                ty::AliasTy {
-                    kind: ty::AliasTyKind::Inherent { def_id: self.def_id },
-                    args: self.args,
-                    _use_alias_ty_new_instead: (),
-                },
-            )
-            .into(),
-            AliasTermKind::OpaqueTy => Ty::new_alias(
-                interner,
-                ty::AliasTy {
-                    kind: ty::AliasTyKind::Opaque { def_id: self.def_id },
-                    args: self.args,
-                    _use_alias_ty_new_instead: (),
-                },
-            )
-            .into(),
-            AliasTermKind::FreeTy => Ty::new_alias(
-                interner,
-                ty::AliasTy {
-                    kind: ty::AliasTyKind::Free { def_id: self.def_id },
-                    args: self.args,
-                    _use_alias_ty_new_instead: (),
-                },
-            )
-            .into(),
+        let alias_ty_kind = match self.kind(interner) {
             AliasTermKind::FreeConst
             | AliasTermKind::InherentConst
             | AliasTermKind::UnevaluatedConst
-            | AliasTermKind::ProjectionConst => I::Const::new_unevaluated(
-                interner,
-                ty::UnevaluatedConst::new(self.def_id.try_into().unwrap(), self.args),
-            )
-            .into(),
-        }
+            | AliasTermKind::ProjectionConst => {
+                return I::Const::new_unevaluated(
+                    interner,
+                    ty::UnevaluatedConst::new(self.def_id.try_into().unwrap(), self.args),
+                )
+                .into();
+            }
+
+            AliasTermKind::ProjectionTy => ty::Projection { def_id: self.def_id },
+            AliasTermKind::InherentTy => ty::Inherent { def_id: self.def_id },
+            AliasTermKind::OpaqueTy => ty::Opaque { def_id: self.def_id },
+            AliasTermKind::FreeTy => ty::Free { def_id: self.def_id },
+        };
+
+        Ty::new_alias(interner, ty::AliasTy::new_from_args(interner, alias_ty_kind, self.args))
+            .into()
     }
 }
 

compiler/rustc_type_ir/src/relate.rs

@@ -504,8 +504,6 @@ pub fn structurally_relate_tys<I: Interner, R: TypeRelation<I>>(
         // Alias tend to mostly already be handled downstream due to normalization.
         (ty::Alias(a), ty::Alias(b)) => {
             let alias_ty = relation.relate(a, b)?;
-            assert_eq!(a.kind, b.kind);
-            assert_eq!(a.kind, alias_ty.kind);
             Ok(Ty::new_alias(cx, alias_ty))
         }
 

compiler/rustc_type_ir/src/ty_kind.rs

@@ -31,25 +31,30 @@ pub enum AliasTyKind<I: Interner> {
     /// A projection `<Type as Trait>::AssocType`.
     ///
     /// Can get normalized away if monomorphic enough.
-    Projection {
-        /// The `DefId` of the `TraitItem` or `ImplItem` for the associated type `N` depending on whether
-        /// this is a projection or an inherent projection or the `DefId` of the `OpaqueType` item if
-        /// this is an opaque.
-        ///
-        /// During codegen, `interner.type_of(def_id)` can be used to get the type of the
-        /// underlying type if the type is an opaque.
-        ///
-        /// Note that if this is an associated type, this is not the `DefId` of the
-        /// `TraitRef` containing this associated type, which is in `interner.associated_item(def_id).container`,
-        /// aka. `interner.parent(def_id)`.
-        def_id: I::DefId,
-    },
+    ///
+    /// The `def_id` is the `DefId` of the `TraitItem` for the associated type.
+    ///
+    /// Note that the `def_id` is not the `DefId` of the `TraitRef` containing this
+    /// associated type, which is in `interner.associated_item(def_id).container`,
+    /// aka. `interner.parent(def_id)`.
+    Projection { def_id: I::DefId },
+
     /// An associated type in an inherent `impl`
+    ///
+    /// The `def_id` is the `DefId` of the `ImplItem` for the associated type.
     Inherent { def_id: I::DefId },
+
     /// An opaque type (usually from `impl Trait` in type aliases or function return types)
     ///
-    /// Can only be normalized away in PostAnalysis mode or its defining scope.
+    /// `def_id` is the `DefId` of the `OpaqueType` item.
+    ///
+    ///
+    /// Can only be normalized away in `PostAnalysis` mode or its defining scope.
+    ///
+    /// During codegen, `interner.type_of(def_id)` can be used to get the type of the
+    /// underlying type if the type is an opaque.
     Opaque { def_id: I::DefId },
+
     /// A type alias that actually checks its trait bounds.
     ///
     /// Currently only used if the type alias references opaque types.