integrate trait aliases into def-paths / metadata

Co-authored-by: Alexander Regueiro <alexreg@me.com>

7 files changed, 20 insertions, 17 deletions

diff --git a/src/librustc/hir/map/def_collector.rs b/src/librustc/hir/map/def_collector.rs
index bc0a64ae7c5..c9b4b2bb997 100644
--- a/src/librustc/hir/map/def_collector.rs
+++ b/src/librustc/hir/map/def_collector.rs
@@ -120,10 +120,10 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
         let def_data = match i.node {
             ItemKind::Impl(..) => DefPathData::Impl,
             ItemKind::Trait(..) => DefPathData::Trait(i.ident.as_interned_str()),
+            ItemKind::TraitAlias(..) => DefPathData::TraitAlias(i.ident.as_interned_str()),
             ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) |
-            ItemKind::TraitAlias(..) | ItemKind::Existential(..) |
-            ItemKind::ExternCrate(..) | ItemKind::ForeignMod(..) | ItemKind::Ty(..) =>
-                DefPathData::TypeNs(i.ident.as_interned_str()),
+            ItemKind::Existential(..) | ItemKind::ExternCrate(..) | ItemKind::ForeignMod(..) |
+            ItemKind::Ty(..) => DefPathData::TypeNs(i.ident.as_interned_str()),
             ItemKind::Mod(..) if i.ident == keywords::Invalid.ident() => {
                 return visit::walk_item(self, i);
             }
diff --git a/src/librustc/hir/map/definitions.rs b/src/librustc/hir/map/definitions.rs
index 6b707dd2dcc..1b744519947 100644
--- a/src/librustc/hir/map/definitions.rs
+++ b/src/librustc/hir/map/definitions.rs
@@ -373,7 +373,9 @@ pub enum DefPathData {
     /// GlobalMetaData identifies a piece of crate metadata that is global to
     /// a whole crate (as opposed to just one item). GlobalMetaData components
     /// are only supposed to show up right below the crate root.
-    GlobalMetaData(InternedString)
+    GlobalMetaData(InternedString),
+    /// A trait alias.
+    TraitAlias(InternedString),
 }
 
 #[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Debug,
@@ -615,6 +617,7 @@ impl DefPathData {
         match *self {
             TypeNs(name) |
             Trait(name) |
+            TraitAlias(name) |
             AssocTypeInTrait(name) |
             AssocTypeInImpl(name) |
             AssocExistentialInImpl(name) |
@@ -642,6 +645,7 @@ impl DefPathData {
         let s = match *self {
             TypeNs(name) |
             Trait(name) |
+            TraitAlias(name) |
             AssocTypeInTrait(name) |
             AssocTypeInImpl(name) |
             AssocExistentialInImpl(name) |
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
index 6db6fe31fba..4d478365e72 100644
--- a/src/librustc/traits/select.rs
+++ b/src/librustc/traits/select.rs
@@ -2154,7 +2154,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
         let def_id = obligation.predicate.def_id();
 
-        if ty::is_trait_alias(self.tcx(), def_id) {
+        if self.tcx().is_trait_alias(def_id) {
             candidates.vec.push(TraitAliasCandidate(def_id.clone()));
         }
 
diff --git a/src/librustc/ty/item_path.rs b/src/librustc/ty/item_path.rs
index 417e14054d2..9328de4f6a0 100644
--- a/src/librustc/ty/item_path.rs
+++ b/src/librustc/ty/item_path.rs
@@ -311,6 +311,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             data @ DefPathData::Misc |
             data @ DefPathData::TypeNs(..) |
             data @ DefPathData::Trait(..) |
+            data @ DefPathData::TraitAlias(..) |
             data @ DefPathData::AssocTypeInTrait(..) |
             data @ DefPathData::AssocTypeInImpl(..) |
             data @ DefPathData::AssocExistentialInImpl(..) |
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index a2c96e7cf9f..e2f696b0974 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -3178,18 +3178,6 @@ pub fn is_impl_trait_defn(tcx: TyCtxt<'_, '_, '_>, def_id: DefId) -> Option<DefI
     None
 }
 
-/// Returns `true` if `def_id` is a trait alias.
-pub fn is_trait_alias(tcx: TyCtxt<'_, '_, '_>, def_id: DefId) -> bool {
-    if let Some(node_id) = tcx.hir().as_local_node_id(def_id) {
-        if let Node::Item(item) = tcx.hir().get(node_id) {
-            if let hir::ItemKind::TraitAlias(..) = item.node {
-                return true;
-            }
-        }
-    }
-    false
-}
-
 /// See `ParamEnv` struct definition for details.
 fn param_env<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                        def_id: DefId)
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index e989ef823e9..75fc0f716a2 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -526,6 +526,15 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
+    /// True if `def_id` refers to a trait alias (i.e., `trait Foo = ...;`).
+    pub fn is_trait_alias(self, def_id: DefId) -> bool {
+        if let DefPathData::TraitAlias(_) = self.def_key(def_id).disambiguated_data.data {
+            true
+        } else {
+            false
+        }
+    }
+
     /// True if this def-id refers to the implicit constructor for
     /// a tuple struct like `struct Foo(u32)`.
     pub fn is_struct_constructor(self, def_id: DefId) -> bool {
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 04e571863d4..51e9192cd29 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -409,6 +409,7 @@ impl PrintContext {
                     DefPathData::AssocTypeInImpl(_) |
                     DefPathData::AssocExistentialInImpl(_) |
                     DefPathData::Trait(_) |
+                    DefPathData::TraitAlias(_) |
                     DefPathData::Impl |
                     DefPathData::TypeNs(_) => {
                         break;