Make calling def_id on a DefSelfTy an error; the previous defids that

were returned, either the trait or the *self type itself*, were not
particularly representative of what the Def is (a type parameter).
Rewrite paths to handle this case specially, just as they handle the
primitive case specifically. This entire `def_id` codepath is kind of a
mess.

src/librustc/middle/dead.rs

@@ -99,6 +99,7 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
                 }
                 _ if self.ignore_non_const_paths => (),
                 def::DefPrimTy(_) => (),
+                def::DefSelfTy(..) => (),
                 def::DefVariant(enum_id, variant_id, _) => {
                     self.check_def_id(enum_id);
                     if !self.ignore_variant_stack.contains(&variant_id) {

src/librustc/middle/def.rs

@@ -135,14 +135,12 @@ impl Def {
             DefFn(id, _) | DefMod(id) | DefForeignMod(id) | DefStatic(id, _) |
             DefVariant(_, id, _) | DefTy(id, _) | DefAssociatedTy(_, id) |
             DefTyParam(_, _, id, _) | DefUse(id) | DefStruct(id) | DefTrait(id) |
-            DefMethod(id) | DefConst(id) | DefAssociatedConst(id) |
+            DefMethod(id) | DefConst(id) | DefAssociatedConst(id) => {
-            DefSelfTy(Some(id), None)=> {
                 id
             }
 
             DefLocal(id) |
-            DefUpvar(id, _, _) |
+            DefUpvar(id, _, _) => {
-            DefSelfTy(_, Some((_, id))) => {
                 DefId::xxx_local(id) // TODO, clearly
             }
 

src/librustc/middle/stability.rs

@@ -474,6 +474,7 @@ pub fn check_path(tcx: &ty::ctxt, path: &hir::Path, id: ast::NodeId,
                   cb: &mut FnMut(DefId, Span, &Option<&Stability>)) {
     match tcx.def_map.borrow().get(&id).map(|d| d.full_def()) {
         Some(def::DefPrimTy(..)) => {}
+        Some(def::DefSelfTy(..)) => {}
         Some(def) => {
             maybe_do_stability_check(tcx, def.def_id(), path.span, cb);
         }

src/librustc_privacy/lib.rs

@@ -263,6 +263,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for EmbargoVisitor<'a, 'tcx> {
                     hir::TyPath(..) => {
                         match self.tcx.def_map.borrow().get(&ty.id).unwrap().full_def() {
                             def::DefPrimTy(..) => true,
+                            def::DefSelfTy(..) => true,
                             def => {
                                 let did = def.def_id();
                                 if let Some(node_id) = self.tcx.map.as_local_node_id(did) {
@@ -337,7 +338,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for EmbargoVisitor<'a, 'tcx> {
             hir::ItemTy(ref ty, _) if public_first => {
                 if let hir::TyPath(..) = ty.node {
                     match self.tcx.def_map.borrow().get(&ty.id).unwrap().full_def() {
-                        def::DefPrimTy(..) | def::DefTyParam(..) => {},
+                        def::DefPrimTy(..) | def::DefSelfTy(..) | def::DefTyParam(..) => {},
                         def => {
                             let did = def.def_id();
                             if let Some(node_id) = self.tcx.map.as_local_node_id(did) {
@@ -1148,7 +1149,7 @@ impl<'a, 'tcx> VisiblePrivateTypesVisitor<'a, 'tcx> {
     fn path_is_private_type(&self, path_id: ast::NodeId) -> bool {
         let did = match self.tcx.def_map.borrow().get(&path_id).map(|d| d.full_def()) {
             // `int` etc. (None doesn't seem to occur.)
-            None | Some(def::DefPrimTy(..)) => return false,
+            None | Some(def::DefPrimTy(..)) | Some(def::DefSelfTy(..)) => return false,
             Some(def) => def.def_id(),
         };
 

src/librustc_trans/save/dump_csv.rs

@@ -235,7 +235,8 @@ impl <'l, 'tcx> DumpCsvVisitor<'l, 'tcx> {
         }
         let def = self.tcx.def_map.borrow().get(&ref_id).unwrap().full_def();
         match def {
-            def::DefPrimTy(_) => None,
+            def::DefPrimTy(..) => None,
+            def::DefSelfTy(..) => None,
             _ => Some(def.def_id()),
         }
     }

src/librustc_trans/save/mod.rs

@@ -637,7 +637,7 @@ impl<'l, 'tcx: 'l> SaveContext<'l, 'tcx> {
         }
         let def = self.tcx.def_map.borrow().get(&ref_id).unwrap().full_def();
         match def {
-            def::DefPrimTy(_) => None,
+            def::DefPrimTy(_) | def::DefSelfTy(..) => None,
             _ => Some(def.def_id()),
         }
     }

src/librustdoc/clean/mod.rs

@@ -2570,17 +2570,19 @@ fn name_from_pat(p: &hir::Pat) -> String {
 fn resolve_type(cx: &DocContext,
                 path: Path,
                 id: ast::NodeId) -> Type {
+    debug!("resolve_type({:?},{:?})", path, id);
     let tcx = match cx.tcx_opt() {
         Some(tcx) => tcx,
         // If we're extracting tests, this return value doesn't matter.
         None => return Primitive(Bool),
     };
-    debug!("searching for {} in defmap", id);
     let def = match tcx.def_map.borrow().get(&id) {
         Some(k) => k.full_def(),
         None => panic!("unresolved id not in defmap")
     };
 
+    debug!("resolve_type: def={:?}", def);
+
     let is_generic = match def {
         def::DefPrimTy(p) => match p {
             hir::TyStr => return Primitive(Str),
@@ -2610,6 +2612,8 @@ fn resolve_type(cx: &DocContext,
 }
 
 fn register_def(cx: &DocContext, def: def::Def) -> DefId {
+    debug!("register_def({:?})", def);
+
     let (did, kind) = match def {
         def::DefFn(i, _) => (i, TypeFunction),
         def::DefTy(i, false) => (i, TypeTypedef),
@@ -2619,6 +2623,8 @@ fn register_def(cx: &DocContext, def: def::Def) -> DefId {
         def::DefMod(i) => (i, TypeModule),
         def::DefStatic(i, _) => (i, TypeStatic),
         def::DefVariant(i, _, _) => (i, TypeEnum),
+        def::DefSelfTy(Some(def_id), _) => (def_id, TypeTrait),
+        def::DefSelfTy(_, Some((impl_id, _))) => return cx.map.local_def_id(impl_id),
         _ => return def.def_id()
     };
     if did.is_local() { return did }