librustc: Stop assuming that implementations and traits only contain

methods.

This paves the way to associated items by introducing an extra level of
abstraction ("impl-or-trait item") between traits/implementations and
methods. This new abstraction is encoded in the metadata and used
throughout the compiler where appropriate.

There are no functional changes; this is purely a refactoring.

src/librustc/front/config.rs

@@ -109,10 +109,14 @@ fn fold_foreign_mod(cx: &mut Context, nm: &ast::ForeignMod) -> ast::ForeignMod {
 
 fn fold_item_underscore(cx: &mut Context, item: &ast::Item_) -> ast::Item_ {
     let item = match *item {
-        ast::ItemImpl(ref a, ref b, c, ref methods) => {
-            let methods = methods.iter().filter(|m| method_in_cfg(cx, &***m))
-                .map(|x| *x).collect();
-            ast::ItemImpl((*a).clone(), (*b).clone(), c, methods)
+        ast::ItemImpl(ref a, ref b, c, ref impl_items) => {
+            let impl_items = impl_items.iter()
+                                       .filter(|ii| {
+                                           impl_item_in_cfg(cx, &**ii)
+                                       })
+                                       .map(|x| *x)
+                                       .collect();
+            ast::ItemImpl((*a).clone(), (*b).clone(), c, impl_items)
         }
         ast::ItemTrait(ref a, ref b, ref c, ref methods) => {
             let methods = methods.iter()
@@ -230,14 +234,16 @@ fn view_item_in_cfg(cx: &mut Context, item: &ast::ViewItem) -> bool {
     return (cx.in_cfg)(item.attrs.as_slice());
 }
 
-fn method_in_cfg(cx: &mut Context, meth: &ast::Method) -> bool {
-    return (cx.in_cfg)(meth.attrs.as_slice());
+fn trait_method_in_cfg(cx: &mut Context, meth: &ast::TraitItem) -> bool {
+    match *meth {
+        ast::RequiredMethod(ref meth) => (cx.in_cfg)(meth.attrs.as_slice()),
+        ast::ProvidedMethod(meth) => (cx.in_cfg)(meth.attrs.as_slice())
+    }
 }
 
-fn trait_method_in_cfg(cx: &mut Context, meth: &ast::TraitMethod) -> bool {
-    match *meth {
-        ast::Required(ref meth) => (cx.in_cfg)(meth.attrs.as_slice()),
-        ast::Provided(meth) => (cx.in_cfg)(meth.attrs.as_slice())
+fn impl_item_in_cfg(cx: &mut Context, impl_item: &ast::ImplItem) -> bool {
+    match *impl_item {
+        ast::MethodImplItem(meth) => (cx.in_cfg)(meth.attrs.as_slice()),
     }
 }
 

src/librustc/lint/builtin.rs

@@ -801,15 +801,19 @@ fn method_context(cx: &Context, m: &ast::Method) -> MethodContext {
         node: m.id
     };
 
-    match cx.tcx.methods.borrow().find_copy(&did) {
+    match cx.tcx.impl_or_trait_items.borrow().find_copy(&did) {
         None => cx.sess().span_bug(m.span, "missing method descriptor?!"),
         Some(md) => {
-            match md.container {
-                ty::TraitContainer(..) => TraitDefaultImpl,
-                ty::ImplContainer(cid) => {
-                    match ty::impl_trait_ref(cx.tcx, cid) {
-                        Some(..) => TraitImpl,
-                        None => PlainImpl
+            match md {
+                ty::MethodTraitItem(md) => {
+                    match md.container {
+                        ty::TraitContainer(..) => TraitDefaultImpl,
+                        ty::ImplContainer(cid) => {
+                            match ty::impl_trait_ref(cx.tcx, cid) {
+                                Some(..) => TraitImpl,
+                                None => PlainImpl
+                            }
+                        }
                     }
                 }
             }
@@ -1470,7 +1474,15 @@ impl LintPass for Stability {
                                 trait_id: trait_id,
                                 method_num: index,
                                 ..
-                            }) => ty::trait_method(cx.tcx, trait_id, index).def_id
+                            }) => {
+                                match ty::trait_item(cx.tcx,
+                                                     trait_id,
+                                                     index) {
+                                    ty::MethodTraitItem(method) => {
+                                        method.def_id
+                                    }
+                                }
+                            }
                         }
                     }
                     None => return

src/librustc/lint/context.rs

@@ -563,9 +563,9 @@ impl<'a> Visitor<()> for Context<'a> {
         visit::walk_generics(self, g, ());
     }
 
-    fn visit_trait_method(&mut self, m: &ast::TraitMethod, _: ()) {
+    fn visit_trait_item(&mut self, m: &ast::TraitItem, _: ()) {
         run_lints!(self, check_trait_method, m);
-        visit::walk_trait_method(self, m, ());
+        visit::walk_trait_item(self, m, ());
     }
 
     fn visit_opt_lifetime_ref(&mut self, sp: Span, lt: &Option<ast::Lifetime>, _: ()) {

src/librustc/lint/mod.rs

@@ -141,7 +141,7 @@ pub trait LintPass {
     fn check_fn(&mut self, _: &Context,
         _: &FnKind, _: &ast::FnDecl, _: &ast::Block, _: Span, _: ast::NodeId) { }
     fn check_ty_method(&mut self, _: &Context, _: &ast::TypeMethod) { }
-    fn check_trait_method(&mut self, _: &Context, _: &ast::TraitMethod) { }
+    fn check_trait_method(&mut self, _: &Context, _: &ast::TraitItem) { }
     fn check_struct_def(&mut self, _: &Context,
         _: &ast::StructDef, _: ast::Ident, _: &ast::Generics, _: ast::NodeId) { }
     fn check_struct_def_post(&mut self, _: &Context,

src/librustc/metadata/common.rs

@@ -77,7 +77,7 @@ pub static tag_crate_dep_hash: uint = 0x1e;
 
 pub static tag_mod_impl: uint = 0x1f;
 
-pub static tag_item_trait_method: uint = 0x20;
+pub static tag_item_trait_item: uint = 0x20;
 
 pub static tag_item_trait_ref: uint = 0x21;
 pub static tag_item_super_trait_ref: uint = 0x22;
@@ -95,14 +95,14 @@ pub static tag_item_field_origin: uint = 0x29;
 
 pub static tag_item_variances: uint = 0x2a;
 /*
-  trait items contain tag_item_trait_method elements,
-  impl items contain tag_item_impl_method elements, and classes
+  trait items contain tag_item_trait_item elements,
+  impl items contain tag_item_impl_item elements, and classes
   have both. That's because some code treats classes like traits,
   and other code treats them like impls. Because classes can contain
-  both, tag_item_trait_method and tag_item_impl_method have to be two
+  both, tag_item_trait_item and tag_item_impl_item have to be two
   different tags.
  */
-pub static tag_item_impl_method: uint = 0x30;
+pub static tag_item_impl_item: uint = 0x30;
 pub static tag_item_trait_method_explicit_self: uint = 0x31;
 
 
@@ -154,9 +154,11 @@ impl astencode_tag {
     }
 }
 
-pub static tag_item_trait_method_sort: uint = 0x60;
+pub static tag_item_trait_item_sort: uint = 0x60;
 
-pub static tag_item_impl_type_basename: uint = 0x61;
+pub static tag_item_trait_parent_sort: uint = 0x61;
+
+pub static tag_item_impl_type_basename: uint = 0x62;
 
 pub static tag_crate_triple: uint = 0x66;
 

src/librustc/metadata/csearch.rs

@@ -16,6 +16,7 @@ use metadata::common::*;
 use metadata::cstore;
 use metadata::decoder;
 use middle::lang_items;
+use middle::resolve;
 use middle::ty;
 use middle::typeck;
 use middle::subst::VecPerParamSpace;
@@ -121,30 +122,33 @@ pub fn get_enum_variants(tcx: &ty::ctxt, def: ast::DefId)
 }
 
 /// Returns information about the given implementation.
-pub fn get_impl_methods(cstore: &cstore::CStore, impl_def_id: ast::DefId)
-                        -> Vec<ast::DefId> {
+pub fn get_impl_items(cstore: &cstore::CStore, impl_def_id: ast::DefId)
+                      -> Vec<ty::ImplOrTraitItemId> {
     let cdata = cstore.get_crate_data(impl_def_id.krate);
-    decoder::get_impl_methods(&*cdata, impl_def_id.node)
+    decoder::get_impl_items(&*cdata, impl_def_id.node)
 }
 
-pub fn get_method(tcx: &ty::ctxt, def: ast::DefId) -> ty::Method {
+pub fn get_impl_or_trait_item(tcx: &ty::ctxt, def: ast::DefId)
+                              -> ty::ImplOrTraitItem {
     let cdata = tcx.sess.cstore.get_crate_data(def.krate);
-    decoder::get_method(tcx.sess.cstore.intr.clone(), &*cdata, def.node, tcx)
+    decoder::get_impl_or_trait_item(tcx.sess.cstore.intr.clone(),
+                                    &*cdata,
+                                    def.node,
+                                    tcx)
 }
 
-pub fn get_method_name_and_explicit_self(cstore: &cstore::CStore,
-                                         def: ast::DefId)
-                                         -> (ast::Ident,
-                                             ty::ExplicitSelfCategory)
-{
+pub fn get_trait_item_name_and_kind(cstore: &cstore::CStore, def: ast::DefId)
+                                    -> (ast::Ident, resolve::TraitItemKind) {
     let cdata = cstore.get_crate_data(def.krate);
-    decoder::get_method_name_and_explicit_self(cstore.intr.clone(), &*cdata, def.node)
+    decoder::get_trait_item_name_and_kind(cstore.intr.clone(),
+                                          &*cdata,
+                                          def.node)
 }
 
-pub fn get_trait_method_def_ids(cstore: &cstore::CStore,
-                                def: ast::DefId) -> Vec<ast::DefId> {
+pub fn get_trait_item_def_ids(cstore: &cstore::CStore, def: ast::DefId)
+                              -> Vec<ty::ImplOrTraitItemId> {
     let cdata = cstore.get_crate_data(def.krate);
-    decoder::get_trait_method_def_ids(&*cdata, def.node)
+    decoder::get_trait_item_def_ids(&*cdata, def.node)
 }
 
 pub fn get_item_variances(cstore: &cstore::CStore,
@@ -286,15 +290,15 @@ pub fn each_implementation_for_trait(cstore: &cstore::CStore,
     decoder::each_implementation_for_trait(&*cdata, def_id.node, callback)
 }
 
-/// If the given def ID describes a method belonging to a trait (either a
+/// If the given def ID describes an item belonging to a trait (either a
 /// default method or an implementation of a trait method), returns the ID of
 /// the trait that the method belongs to. Otherwise, returns `None`.
-pub fn get_trait_of_method(cstore: &cstore::CStore,
-                           def_id: ast::DefId,
-                           tcx: &ty::ctxt)
-                           -> Option<ast::DefId> {
+pub fn get_trait_of_item(cstore: &cstore::CStore,
+                         def_id: ast::DefId,
+                         tcx: &ty::ctxt)
+                         -> Option<ast::DefId> {
     let cdata = cstore.get_crate_data(def_id.krate);
-    decoder::get_trait_of_method(&*cdata, def_id.node, tcx)
+    decoder::get_trait_of_item(&*cdata, def_id.node, tcx)
 }
 
 pub fn get_tuple_struct_definition_if_ctor(cstore: &cstore::CStore,