add trait aliases to HIR

src/librustc/hir/def.rs

@@ -37,6 +37,7 @@ pub enum Def {
     Trait(DefId),
     TyAlias(DefId),
     TyForeign(DefId),
+    TraitAlias(DefId),
     AssociatedTy(DefId),
     PrimTy(hir::PrimTy),
     TyParam(DefId),
@@ -155,7 +156,8 @@ impl Def {
     pub fn def_id(&self) -> DefId {
         match *self {
             Def::Fn(id) | Def::Mod(id) | Def::Static(id, _) |
-            Def::Variant(id) | Def::VariantCtor(id, ..) | Def::Enum(id) | Def::TyAlias(id) |
+            Def::Variant(id) | Def::VariantCtor(id, ..) | Def::Enum(id) |
+            Def::TyAlias(id) | Def::TraitAlias(id) |
             Def::AssociatedTy(id) | Def::TyParam(id) | Def::Struct(id) | Def::StructCtor(id, ..) |
             Def::Union(id) | Def::Trait(id) | Def::Method(id) | Def::Const(id) |
             Def::AssociatedConst(id) | Def::Macro(id, ..) |
@@ -186,6 +188,7 @@ pub fn kind_name(&self) -> &'static str {
             Def::VariantCtor(.., CtorKind::Fictive) => "struct variant",
             Def::Enum(..) => "enum",
             Def::TyAlias(..) => "type alias",
+            Def::TraitAlias(..) => "trait alias",
             Def::AssociatedTy(..) => "associated type",
             Def::Struct(..) => "struct",
             Def::StructCtor(.., CtorKind::Fn) => "tuple struct",

src/librustc/hir/intravisit.rs

@@ -526,6 +526,11 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
             walk_list!(visitor, visit_ty_param_bound, bounds);
             walk_list!(visitor, visit_trait_item_ref, trait_item_refs);
         }
+        ItemTraitAlias(ref generics, ref bounds) => {
+            visitor.visit_id(item.id);
+            visitor.visit_generics(generics);
+            walk_list!(visitor, visit_ty_param_bound, bounds);
+        }
     }
     walk_list!(visitor, visit_attribute, &item.attrs);
 }

src/librustc/hir/lowering.rs

@@ -1924,9 +1924,11 @@ fn lower_item_kind(&mut self,
                                bounds,
                                items)
             }
-            ItemKind::MacroDef(..) | ItemKind::Mac(..) => {
-                panic!("Shouldn't still be around")
+            ItemKind::TraitAlias(ref generics, ref bounds) => {
+                hir::ItemTraitAlias(self.lower_generics(generics),
+                                    self.lower_bounds(bounds, ImplTraitContext::Disallowed))
             }
+            ItemKind::MacroDef(..) | ItemKind::Mac(..) => panic!("Shouldn't still be around"),
         }
 
         // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to

src/librustc/hir/map/def_collector.rs

@@ -106,7 +106,8 @@ fn visit_item(&mut self, i: &'a Item) {
         let def_data = match i.node {
             ItemKind::AutoImpl(..) | ItemKind::Impl(..) =>
                 DefPathData::Impl,
-            ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) | ItemKind::Trait(..) |
+            ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) |
+            ItemKind::Trait(..) | ItemKind::TraitAlias(..) |
             ItemKind::ExternCrate(..) | ItemKind::ForeignMod(..) | ItemKind::Ty(..) =>
                 DefPathData::TypeNs(i.ident.name.as_str()),
             ItemKind::Mod(..) if i.ident == keywords::Invalid.ident() => {

src/librustc/hir/map/mod.rs

@@ -1185,6 +1185,7 @@ fn node_id_to_string(map: &Map, id: NodeId, include_id: bool) -> String {
                 ItemStruct(..) => "struct",
                 ItemUnion(..) => "union",
                 ItemTrait(..) => "trait",
+                ItemTraitAlias(..) => "trait alias",
                 ItemImpl(..) => "impl",
                 ItemAutoImpl(..) => "default impl",
             };

src/librustc/hir/mod.rs

@@ -1888,6 +1888,8 @@ pub enum Item_ {
     ItemUnion(VariantData, Generics),
     /// Represents a Trait Declaration
     ItemTrait(IsAuto, Unsafety, Generics, TyParamBounds, HirVec<TraitItemRef>),
+    /// Represents a Trait Alias Declaration
+    ItemTraitAlias(Generics, TyParamBounds),
 
     /// Auto trait implementations
     ///
@@ -1919,6 +1921,7 @@ pub fn descriptive_variant(&self) -> &str {
             ItemStruct(..) => "struct",
             ItemUnion(..) => "union",
             ItemTrait(..) => "trait",
+            ItemTraitAlias(..) => "trait alias",
             ItemImpl(..) |
             ItemAutoImpl(..) => "item",
         }

src/librustc/hir/print.rs

@@ -747,6 +747,27 @@ pub fn print_item(&mut self, item: &hir::Item) -> io::Result<()> {
                 }
                 self.bclose(item.span)?;
             }
+            hir::ItemTraitAlias(ref generics, ref bounds) => {
+                self.head("")?;
+                self.print_visibility(&item.vis)?;
+                self.word_nbsp("trait")?;
+                self.print_name(item.name)?;
+                self.print_generics(generics)?;
+                let mut real_bounds = Vec::with_capacity(bounds.len());
+                // FIXME(durka) this seems to be some quite outdated syntax
+                for b in bounds.iter() {
+                    if let TraitTyParamBound(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
+                        self.s.space()?;
+                        self.word_space("for ?")?;
+                        self.print_trait_ref(&ptr.trait_ref)?;
+                    } else {
+                        real_bounds.push(b.clone());
+                    }
+                }
+                self.print_bounds(" = ", &real_bounds[..])?;
+                self.print_where_clause(&generics.where_clause)?;
+                self.s.word(";")?;
+            }
         }
         self.ann.post(self, NodeItem(item))
     }

src/librustc/ich/impls_hir.rs

@@ -848,6 +848,7 @@ fn hash_stable<W: StableHasherResult>(&self,
     ItemStruct(variant_data, generics),
     ItemUnion(variant_data, generics),
     ItemTrait(is_auto, unsafety, generics, bounds, item_refs),
+    ItemTraitAlias(generics, bounds),
     ItemAutoImpl(unsafety, trait_ref),
     ItemImpl(unsafety, impl_polarity, impl_defaultness, generics, trait_ref, ty, impl_item_refs)
 });
@@ -1004,6 +1005,7 @@ fn hash_stable<W: StableHasherResult>(&self,
     Variant(def_id),
     Trait(def_id),
     TyAlias(def_id),
+    TraitAlias(def_id),
     AssociatedTy(def_id),
     PrimTy(prim_ty),
     TyParam(def_id),

src/librustc/middle/reachable.rs

@@ -268,7 +268,7 @@ fn propagate_node(&mut self, node: &hir_map::Node<'tcx>,
                     hir::ItemExternCrate(_) | hir::ItemUse(..) |
                     hir::ItemTy(..) | hir::ItemStatic(..) |
                     hir::ItemMod(..) | hir::ItemForeignMod(..) |
-                    hir::ItemImpl(..) | hir::ItemTrait(..) |
+                    hir::ItemImpl(..) | hir::ItemTrait(..) | hir::ItemTraitAlias(..) |
                     hir::ItemStruct(..) | hir::ItemEnum(..) |
                     hir::ItemUnion(..) | hir::ItemAutoImpl(..) |
                     hir::ItemGlobalAsm(..) => {}

src/librustc/middle/resolve_lifetime.rs

@@ -469,6 +469,7 @@ fn visit_item(&mut self, item: &'tcx hir::Item) {
             | hir::ItemStruct(_, ref generics)
             | hir::ItemUnion(_, ref generics)
             | hir::ItemTrait(_, _, ref generics, ..)
+            | hir::ItemTraitAlias(ref generics, ..)
             | hir::ItemImpl(_, _, _, ref generics, ..) => {
                 // These kinds of items have only early bound lifetime parameters.
                 let mut index = if let hir::ItemTrait(..) = item.node {

src/librustc_metadata/encoder.rs

@@ -979,6 +979,7 @@ fn encode_info_for_item(&mut self, (def_id, item): (DefId, &'tcx hir::Item)) ->
                 EntryKind::Trait(self.lazy(&data))
             }
             hir::ItemExternCrate(_) |
+            hir::ItemTraitAlias(..) |
             hir::ItemUse(..) => bug!("cannot encode info for item {:?}", item),
         };
 
@@ -1526,7 +1527,8 @@ fn encode_addl_info_for_item(&mut self, item: &hir::Item) {
             hir::ItemExternCrate(..) |
             hir::ItemUse(..) |
             hir::ItemAutoImpl(..) |
-            hir::ItemTy(..) => {
+            hir::ItemTy(..) |
+            hir::ItemTraitAlias(..) => {
                 // no sub-item recording needed in these cases
             }
             hir::ItemEnum(..) => {

src/librustc_privacy/lib.rs

@@ -158,7 +158,8 @@ fn visit_item(&mut self, item: &'tcx hir::Item) {
             // Other `pub` items inherit levels from parents
             hir::ItemConst(..) | hir::ItemEnum(..) | hir::ItemExternCrate(..) |
             hir::ItemGlobalAsm(..) | hir::ItemFn(..) | hir::ItemMod(..) |
-            hir::ItemStatic(..) | hir::ItemStruct(..) | hir::ItemTrait(..) |
+            hir::ItemStatic(..) | hir::ItemStruct(..) |
+            hir::ItemTrait(..) | hir::ItemTraitAlias(..) |
             hir::ItemTy(..) | hir::ItemUnion(..) | hir::ItemUse(..) => {
                 if item.vis == hir::Public { self.prev_level } else { None }
             }
@@ -212,7 +213,7 @@ fn visit_item(&mut self, item: &'tcx hir::Item) {
                 }
             }
             hir::ItemUse(..) | hir::ItemStatic(..) | hir::ItemConst(..) |
-            hir::ItemGlobalAsm(..) | hir::ItemTy(..) | hir::ItemMod(..) |
+            hir::ItemGlobalAsm(..) | hir::ItemTy(..) | hir::ItemMod(..) | hir::ItemTraitAlias(..) |
             hir::ItemFn(..) | hir::ItemExternCrate(..) | hir::ItemAutoImpl(..) => {}
         }
 
@@ -252,6 +253,11 @@ fn visit_item(&mut self, item: &'tcx hir::Item) {
                     }
                 }
             }
+            hir::ItemTraitAlias(..) => {
+                if item_level.is_some() {
+                    self.reach(item.id).generics().predicates();
+                }
+            }
             // Visit everything except for private impl items
             hir::ItemImpl(.., ref trait_ref, _, ref impl_item_refs) => {
                 if item_level.is_some() {
@@ -1498,6 +1504,9 @@ fn visit_item(&mut self, item: &'tcx hir::Item) {
                     }
                 }
             }
+            hir::ItemTraitAlias(..) => {
+                self.check(item.id, item_visibility).generics().predicates();
+            }
             hir::ItemEnum(ref def, _) => {
                 self.check(item.id, item_visibility).generics().predicates();
 

src/librustc_trans_utils/collector.rs

@@ -894,6 +894,7 @@ fn visit_item(&mut self, item: &'v hir::Item) {
             hir::ItemTy(..)          |
             hir::ItemAutoImpl(..) |
             hir::ItemTrait(..)       |
+            hir::ItemTraitAlias(..)  |
             hir::ItemMod(..)         => {
                 // Nothing to do, just keep recursing...
             }