syntax: add fully qualified UFCS expressions.

25 files changed, 89 insertions, 42 deletions

diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index d95000ece5a..59808b302f4 100644
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -1731,7 +1731,7 @@ impl LintPass for Stability {
         let mut span = e.span;
 
         let id = match e.node {
-            ast::ExprPath(..) | ast::ExprStruct(..) => {
+            ast::ExprPath(..) | ast::ExprQPath(..) | ast::ExprStruct(..) => {
                 match cx.tcx.def_map.borrow().get(&e.id) {
                     Some(&def) => def.def_id(),
                     None => return
diff --git a/src/librustc/middle/cfg/construct.rs b/src/librustc/middle/cfg/construct.rs
index b601ea59486..07b520e5865 100644
--- a/src/librustc/middle/cfg/construct.rs
+++ b/src/librustc/middle/cfg/construct.rs
@@ -495,7 +495,8 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             ast::ExprMac(..) |
             ast::ExprClosure(..) |
             ast::ExprLit(..) |
-            ast::ExprPath(..) => {
+            ast::ExprPath(..) |
+            ast::ExprQPath(..) => {
                 self.straightline(expr, pred, None::<ast::Expr>.iter())
             }
         }
diff --git a/src/librustc/middle/check_const.rs b/src/librustc/middle/check_const.rs
index 621d7274b3f..202020a9033 100644
--- a/src/librustc/middle/check_const.rs
+++ b/src/librustc/middle/check_const.rs
@@ -111,7 +111,7 @@ fn check_expr(v: &mut CheckCrateVisitor, e: &ast::Expr) {
                            expression");
             }
         }
-        ast::ExprPath(_) => {
+        ast::ExprPath(_) | ast::ExprQPath(_) => {
             match v.tcx.def_map.borrow()[e.id] {
                 DefStatic(..) | DefConst(..) |
                 DefFn(..) | DefStaticMethod(..) | DefMethod(..) |
diff --git a/src/librustc/middle/check_static.rs b/src/librustc/middle/check_static.rs
index 154272d2deb..026aa3c5ccf 100644
--- a/src/librustc/middle/check_static.rs
+++ b/src/librustc/middle/check_static.rs
@@ -228,7 +228,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for CheckStaticVisitor<'a, 'tcx> {
                           "{} are not allowed to have custom pointers",
                           self.msg());
             }
-            ast::ExprPath(..) => {
+            ast::ExprPath(_) | ast::ExprQPath(_) => {
                 match ty::resolve_expr(self.tcx, e) {
                     def::DefStatic(..) if self.mode == InConstant => {
                         let msg = "constants cannot refer to other statics, \
diff --git a/src/librustc/middle/check_static_recursion.rs b/src/librustc/middle/check_static_recursion.rs
index e2a0738def1..86a58dae45a 100644
--- a/src/librustc/middle/check_static_recursion.rs
+++ b/src/librustc/middle/check_static_recursion.rs
@@ -93,7 +93,7 @@ impl<'a, 'ast, 'v> Visitor<'v> for CheckItemRecursionVisitor<'a, 'ast> {
 
     fn visit_expr(&mut self, e: &ast::Expr) {
         match e.node {
-            ast::ExprPath(..) => {
+            ast::ExprPath(_) | ast::ExprQPath(_) => {
                 match self.def_map.borrow().get(&e.id) {
                     Some(&DefStatic(def_id, _)) |
                     Some(&DefConst(def_id)) if
diff --git a/src/librustc/middle/const_eval.rs b/src/librustc/middle/const_eval.rs
index 52352e920ce..c998d178c22 100644
--- a/src/librustc/middle/const_eval.rs
+++ b/src/librustc/middle/const_eval.rs
@@ -244,7 +244,7 @@ impl<'a, 'tcx> ConstEvalVisitor<'a, 'tcx> {
 
             // FIXME: (#3728) we can probably do something CCI-ish
             // surrounding nonlocal constants. But we don't yet.
-            ast::ExprPath(_) => self.lookup_constness(e),
+            ast::ExprPath(_) | ast::ExprQPath(_) => self.lookup_constness(e),
 
             ast::ExprRepeat(..) => general_const,
 
@@ -356,6 +356,13 @@ pub fn const_expr_to_pat(tcx: &ty::ctxt, expr: &Expr) -> P<ast::Pat> {
             }
         }
 
+        ast::ExprQPath(_) => {
+            match lookup_const(tcx, expr) {
+                Some(actual) => return const_expr_to_pat(tcx, actual),
+                _ => unreachable!()
+            }
+        }
+
         _ => ast::PatLit(P(expr.clone()))
     };
     P(ast::Pat { id: expr.id, node: pat, span: expr.span })
@@ -542,7 +549,7 @@ pub fn eval_const_expr_partial(tcx: &ty::ctxt, e: &Expr) -> Result<const_val, St
                 ty::ty_float(ast::TyF64) => (f64, const_float, f64)
             }))
       }
-      ast::ExprPath(_) => {
+      ast::ExprPath(_) | ast::ExprQPath(_) => {
           match lookup_const(tcx, e) {
               Some(actual_e) => eval_const_expr_partial(tcx, &*actual_e),
               None => Err("non-constant path in constant expr".to_string())
diff --git a/src/librustc/middle/effect.rs b/src/librustc/middle/effect.rs
index f7eea6e5cb7..abb8f35f662 100644
--- a/src/librustc/middle/effect.rs
+++ b/src/librustc/middle/effect.rs
@@ -175,7 +175,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for EffectCheckVisitor<'a, 'tcx> {
             ast::ExprInlineAsm(..) => {
                 self.require_unsafe(expr.span, "use of inline assembly");
             }
-            ast::ExprPath(..) => {
+            ast::ExprPath(_) | ast::ExprQPath(_) => {
                 if let def::DefStatic(_, true) = ty::resolve_expr(self.tcx, expr) {
                     self.require_unsafe(expr.span, "use of mutable static");
                 }
diff --git a/src/librustc/middle/expr_use_visitor.rs b/src/librustc/middle/expr_use_visitor.rs
index e5eb439d42c..a5f2dc398e9 100644
--- a/src/librustc/middle/expr_use_visitor.rs
+++ b/src/librustc/middle/expr_use_visitor.rs
@@ -424,7 +424,7 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,'tcx,TYPER> {
                 self.walk_expr(&**subexpr)
             }
 
-            ast::ExprPath(..) => { }
+            ast::ExprPath(_) | ast::ExprQPath(_) => { }
 
             ast::ExprUnary(ast::UnDeref, ref base) => {      // *base
                 if !self.walk_overloaded_operator(expr, &**base, Vec::new(), PassArgs::ByRef) {
diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index 1b1dca00422..6b9e5b2ceea 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -447,7 +447,7 @@ fn visit_arm(ir: &mut IrMaps, arm: &ast::Arm) {
 fn visit_expr(ir: &mut IrMaps, expr: &Expr) {
     match expr.node {
       // live nodes required for uses or definitions of variables:
-      ast::ExprPath(_) => {
+      ast::ExprPath(_) | ast::ExprQPath(_) => {
         let def = ir.tcx.def_map.borrow()[expr.id].clone();
         debug!("expr {}: path that leads to {:?}", expr.id, def);
         if let DefLocal(..) = def {
@@ -960,7 +960,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         match expr.node {
           // Interesting cases with control flow or which gen/kill
 
-          ast::ExprPath(_) => {
+          ast::ExprPath(_) | ast::ExprQPath(_) => {
               self.access_path(expr, succ, ACC_READ | ACC_USE)
           }
 
@@ -1289,7 +1289,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         // just ignore such cases and treat them as reads.
 
         match expr.node {
-            ast::ExprPath(_) => succ,
+            ast::ExprPath(_) | ast::ExprQPath(_) => succ,
             ast::ExprField(ref e, _) => self.propagate_through_expr(&**e, succ),
             ast::ExprTupField(ref e, _) => self.propagate_through_expr(&**e, succ),
             _ => self.propagate_through_expr(expr, succ)
@@ -1300,7 +1300,9 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
     fn write_lvalue(&mut self, expr: &Expr, succ: LiveNode, acc: uint)
                     -> LiveNode {
         match expr.node {
-          ast::ExprPath(_) => self.access_path(expr, succ, acc),
+          ast::ExprPath(_) | ast::ExprQPath(_) => {
+              self.access_path(expr, succ, acc)
+          }
 
           // We do not track other lvalues, so just propagate through
           // to their subcomponents.  Also, it may happen that
@@ -1492,7 +1494,7 @@ fn check_expr(this: &mut Liveness, expr: &Expr) {
       ast::ExprBlock(..) | ast::ExprMac(..) | ast::ExprAddrOf(..) |
       ast::ExprStruct(..) | ast::ExprRepeat(..) | ast::ExprParen(..) |
       ast::ExprClosure(..) | ast::ExprPath(..) | ast::ExprBox(..) |
-      ast::ExprRange(..) => {
+      ast::ExprRange(..) | ast::ExprQPath(..) => {
         visit::walk_expr(this, expr);
       }
       ast::ExprIfLet(..) => {
@@ -1583,7 +1585,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 
     fn check_lvalue(&mut self, expr: &Expr) {
         match expr.node {
-            ast::ExprPath(_) => {
+            ast::ExprPath(_) | ast::ExprQPath(_) => {
                 if let DefLocal(nid) = self.ir.tcx.def_map.borrow()[expr.id].clone() {
                     // Assignment to an immutable variable or argument: only legal
                     // if there is no later assignment. If this local is actually
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 51ec7528432..90fe6b49911 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -520,7 +520,7 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
             }
           }
 
-          ast::ExprPath(_) => {
+          ast::ExprPath(_) | ast::ExprQPath(_) => {
             let def = (*self.tcx().def_map.borrow())[expr.id];
             self.cat_def(expr.id, expr.span, expr_ty, def)
           }
diff --git a/src/librustc/middle/privacy.rs b/src/librustc/middle/privacy.rs
index aa37c2fe348..b92870cfa42 100644
--- a/src/librustc/middle/privacy.rs
+++ b/src/librustc/middle/privacy.rs
@@ -920,7 +920,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for PrivacyVisitor<'a, 'tcx> {
                                                             struct type?!"),
                 }
             }
-            ast::ExprPath(..) => {
+            ast::ExprPath(_) | ast::ExprQPath(_) => {
                 let guard = |&: did: ast::DefId| {
                     let fields = ty::lookup_struct_fields(self.tcx, did);
                     let any_priv = fields.iter().any(|f| {
diff --git a/src/librustc/middle/reachable.rs b/src/librustc/middle/reachable.rs
index 906607ddc5b..b7e6da8c5f6 100644
--- a/src/librustc/middle/reachable.rs
+++ b/src/librustc/middle/reachable.rs
@@ -104,7 +104,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for ReachableContext<'a, 'tcx> {
     fn visit_expr(&mut self, expr: &ast::Expr) {
 
         match expr.node {
-            ast::ExprPath(_) => {
+            ast::ExprPath(_) | ast::ExprQPath(_) => {
                 let def = match self.tcx.def_map.borrow().get(&expr.id) {
                     Some(&def) => def,
                     None => {
diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index 755983c71bb..525fe86cf24 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -4515,7 +4515,7 @@ pub fn expr_kind(tcx: &ctxt, expr: &ast::Expr) -> ExprKind {
     }
 
     match expr.node {
-        ast::ExprPath(..) => {
+        ast::ExprPath(_) | ast::ExprQPath(_) => {
             match resolve_expr(tcx, expr) {
                 def::DefVariant(tid, vid, _) => {
                     let variant_info = enum_variant_with_id(tcx, tid, vid);
diff --git a/src/librustc_back/svh.rs b/src/librustc_back/svh.rs
index 4e260da2e4d..789a87bbcda 100644
--- a/src/librustc_back/svh.rs
+++ b/src/librustc_back/svh.rs
@@ -252,6 +252,7 @@ mod svh_visitor {
         SawExprIndex,
         SawExprRange,
         SawExprPath,
+        SawExprQPath,
         SawExprAddrOf(ast::Mutability),
         SawExprRet,
         SawExprInlineAsm(&'a ast::InlineAsm),
@@ -285,6 +286,7 @@ mod svh_visitor {
             ExprIndex(..)            => SawExprIndex,
             ExprRange(..)            => SawExprRange,
             ExprPath(..)             => SawExprPath,
+            ExprQPath(..)            => SawExprQPath,
             ExprAddrOf(m, _)         => SawExprAddrOf(m),
             ExprBreak(id)            => SawExprBreak(id.map(content)),
             ExprAgain(id)            => SawExprAgain(id.map(content)),
diff --git a/src/librustc_trans/trans/_match.rs b/src/librustc_trans/trans/_match.rs
index f182045efd2..b01604bd397 100644
--- a/src/librustc_trans/trans/_match.rs
+++ b/src/librustc_trans/trans/_match.rs
@@ -1235,7 +1235,7 @@ pub fn trans_match<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 /// Checks whether the binding in `discr` is assigned to anywhere in the expression `body`
 fn is_discr_reassigned(bcx: Block, discr: &ast::Expr, body: &ast::Expr) -> bool {
     let (vid, field) = match discr.node {
-        ast::ExprPath(..) => match bcx.def(discr.id) {
+        ast::ExprPath(_) | ast::ExprQPath(_) => match bcx.def(discr.id) {
             def::DefLocal(vid) | def::DefUpvar(vid, _, _) => (vid, None),
             _ => return false
         },
diff --git a/src/librustc_trans/trans/callee.rs b/src/librustc_trans/trans/callee.rs
index 6196f9e5eab..11006f37531 100644
--- a/src/librustc_trans/trans/callee.rs
+++ b/src/librustc_trans/trans/callee.rs
@@ -91,8 +91,11 @@ fn trans<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, expr: &ast::Expr)
     debug!("callee::trans(expr={})", expr.repr(bcx.tcx()));
 
     // pick out special kinds of expressions that can be called:
-    if let ast::ExprPath(_) = expr.node {
-        return trans_def(bcx, bcx.def(expr.id), expr);
+    match expr.node {
+        ast::ExprPath(_) | ast::ExprQPath(_) => {
+            return trans_def(bcx, bcx.def(expr.id), expr);
+        }
+        _ => {}
     }
 
     // any other expressions are closures:
diff --git a/src/librustc_trans/trans/consts.rs b/src/librustc_trans/trans/consts.rs
index 00b97286de3..29cf9f72ef8 100644
--- a/src/librustc_trans/trans/consts.rs
+++ b/src/librustc_trans/trans/consts.rs
@@ -600,7 +600,7 @@ fn const_expr_unadjusted(cx: &CrateContext, e: &ast::Expr) -> ValueRef {
                 C_array(llunitty, &vs[])
             }
           }
-          ast::ExprPath(_) => {
+          ast::ExprPath(_) | ast::ExprQPath(_) => {
             let def = cx.tcx().def_map.borrow()[e.id];
             match def {
                 def::DefFn(..) | def::DefStaticMethod(..) | def::DefMethod(..) => {
diff --git a/src/librustc_trans/trans/debuginfo.rs b/src/librustc_trans/trans/debuginfo.rs
index 5bbd83344bf..d5416ae0631 100644
--- a/src/librustc_trans/trans/debuginfo.rs
+++ b/src/librustc_trans/trans/debuginfo.rs
@@ -3526,7 +3526,8 @@ fn create_scope_map(cx: &CrateContext,
             ast::ExprLit(_)   |
             ast::ExprBreak(_) |
             ast::ExprAgain(_) |
-            ast::ExprPath(_)  => {}
+            ast::ExprPath(_)  |
+            ast::ExprQPath(_) => {}
 
             ast::ExprCast(ref sub_exp, _)     |
             ast::ExprAddrOf(_, ref sub_exp)  |
diff --git a/src/librustc_trans/trans/expr.rs b/src/librustc_trans/trans/expr.rs
index ac50445be2f..0e921d8e522 100644
--- a/src/librustc_trans/trans/expr.rs
+++ b/src/librustc_trans/trans/expr.rs
@@ -564,7 +564,7 @@ fn trans_datum_unadjusted<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         ast::ExprParen(ref e) => {
             trans(bcx, &**e)
         }
-        ast::ExprPath(_) => {
+        ast::ExprPath(_) | ast::ExprQPath(_) => {
             trans_def(bcx, expr, bcx.def(expr.id))
         }
         ast::ExprField(ref base, ident) => {
@@ -997,7 +997,7 @@ fn trans_rvalue_dps_unadjusted<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         ast::ExprParen(ref e) => {
             trans_into(bcx, &**e, dest)
         }
-        ast::ExprPath(_) => {
+        ast::ExprPath(_) | ast::ExprQPath(_) => {
             trans_def_dps_unadjusted(bcx, expr, bcx.def(expr.id), dest)
         }
         ast::ExprIf(ref cond, ref thn, ref els) => {
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 45e05c12713..27d31a3a2f7 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -1001,9 +1001,12 @@ fn qpath_to_ty<'tcx>(this: &AstConv<'tcx>,
 
     debug!("qpath_to_ty: trait_ref={}", trait_ref.repr(this.tcx()));
 
+    // `<T as Trait>::U<V>` shouldn't parse right now.
+    assert!(qpath.item_path.parameters.is_empty());
+
     return this.projected_ty(ast_ty.span,
                              trait_ref,
-                             qpath.item_name.name);
+                             qpath.item_path.identifier.name);
 }
 
 // Parses the programmer's textual representation of a type into our
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index b65e1d1d664..8dc3adad3b2 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1614,7 +1614,7 @@ impl<'tcx> Clean<Type> for ty::Ty<'tcx> {
 impl Clean<Type> for ast::QPath {
     fn clean(&self, cx: &DocContext) -> Type {
         Type::QPath {
-            name: self.item_name.clean(cx),
+            name: self.item_path.identifier.clean(cx),
             self_type: box self.self_type.clean(cx),
             trait_: box self.trait_ref.clean(cx)
         }
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index c2cfa484aff..61bc1865517 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -747,6 +747,8 @@ pub enum Expr_ {
     /// Variable reference, possibly containing `::` and/or
     /// type parameters, e.g. foo::bar::<baz>
     ExprPath(Path),
+    /// A "qualified path", e.g. `<Vec<T> as SomeTrait>::SomeType`
+    ExprQPath(P<QPath>),
 
     ExprAddrOf(Mutability, P<Expr>),
     ExprBreak(Option<Ident>),
@@ -771,12 +773,12 @@ pub enum Expr_ {
 ///
 ///     <Vec<T> as SomeTrait>::SomeAssociatedItem
 ///      ^~~~~     ^~~~~~~~~   ^~~~~~~~~~~~~~~~~~
-///      self_type  trait_name  item_name
+///      self_type  trait_name  item_path
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Show)]
 pub struct QPath {
     pub self_type: P<Ty>,
     pub trait_ref: P<TraitRef>,
-    pub item_name: Ident, // FIXME(#20301) -- should use Name
+    pub item_path: PathSegment,
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Show, Copy)]
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index c45a4005339..2a704349295 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -454,7 +454,10 @@ pub fn noop_fold_qpath<T: Folder>(qpath: P<QPath>, fld: &mut T) -> P<QPath> {
         QPath {
             self_type: fld.fold_ty(qpath.self_type),
             trait_ref: qpath.trait_ref.map(|tr| fld.fold_trait_ref(tr)),
-            item_name: fld.fold_ident(qpath.item_name),
+            item_path: PathSegment {
+                identifier: fld.fold_ident(qpath.item_path.identifier),
+                parameters: fld.fold_path_parameters(qpath.item_path.parameters),
+            }
         }
     })
 }
@@ -1381,6 +1384,7 @@ pub fn noop_fold_expr<T: Folder>(Expr {id, node, span}: Expr, folder: &mut T) ->
                           e2.map(|x| folder.fold_expr(x)))
             }
             ExprPath(pth) => ExprPath(folder.fold_path(pth)),
+            ExprQPath(qpath) => ExprQPath(folder.fold_qpath(qpath)),
             ExprBreak(opt_ident) => ExprBreak(opt_ident.map(|x| folder.fold_ident(x))),
             ExprAgain(opt_ident) => ExprAgain(opt_ident.map(|x| folder.fold_ident(x))),
             ExprRet(e) => ExprRet(e.map(|x| folder.fold_expr(x))),
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 9b6f8e6002d..ec6672d22a9 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -727,14 +727,7 @@ impl<'a> State<'a> {
                 try!(self.print_bounds("", &bounds[]));
             }
             ast::TyQPath(ref qpath) => {
-                try!(word(&mut self.s, "<"));
-                try!(self.print_type(&*qpath.self_type));
-                try!(space(&mut self.s));
-                try!(self.word_space("as"));
-                try!(self.print_trait_ref(&*qpath.trait_ref));
-                try!(word(&mut self.s, ">"));
-                try!(word(&mut self.s, "::"));
-                try!(self.print_ident(qpath.item_name));
+                try!(self.print_qpath(&**qpath, false))
             }
             ast::TyFixedLengthVec(ref ty, ref v) => {
                 try!(word(&mut self.s, "["));
@@ -1749,6 +1742,7 @@ impl<'a> State<'a> {
                 }
             }
             ast::ExprPath(ref path) => try!(self.print_path(path, true)),
+            ast::ExprQPath(ref qpath) => try!(self.print_qpath(&**qpath, true)),
             ast::ExprBreak(opt_ident) => {
                 try!(word(&mut self.s, "break"));
                 try!(space(&mut self.s));
@@ -1933,6 +1927,22 @@ impl<'a> State<'a> {
         Ok(())
     }
 
+    fn print_qpath(&mut self,
+                   qpath: &ast::QPath,
+                   colons_before_params: bool)
+                   -> IoResult<()>
+    {
+        try!(word(&mut self.s, "<"));
+        try!(self.print_type(&*qpath.self_type));
+        try!(space(&mut self.s));
+        try!(self.word_space("as"));
+        try!(self.print_trait_ref(&*qpath.trait_ref));
+        try!(word(&mut self.s, ">"));
+        try!(word(&mut self.s, "::"));
+        try!(self.print_ident(qpath.item_path.identifier));
+        self.print_path_parameters(&qpath.item_path.parameters, colons_before_params)
+    }
+
     fn print_path_parameters(&mut self,
                              parameters: &ast::PathParameters,
                              colons_before_params: bool)
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 3f91304dcc5..7778b4fa34a 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -126,6 +126,9 @@ pub trait Visitor<'v> : Sized {
     fn visit_path(&mut self, path: &'v Path, _id: ast::NodeId) {
         walk_path(self, path)
     }
+    fn visit_qpath(&mut self, qpath_span: Span, qpath: &'v QPath) {
+        walk_qpath(self, qpath_span, qpath)
+    }
     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'v PathSegment) {
         walk_path_segment(self, path_span, path_segment)
     }
@@ -419,9 +422,7 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty) {
             walk_ty_param_bounds_helper(visitor, bounds);
         }
         TyQPath(ref qpath) => {
-            visitor.visit_ty(&*qpath.self_type);
-            visitor.visit_trait_ref(&*qpath.trait_ref);
-            visitor.visit_ident(typ.span, qpath.item_name);
+            visitor.visit_qpath(typ.span, &**qpath);
         }
         TyFixedLengthVec(ref ty, ref expression) => {
             visitor.visit_ty(&**ty);
@@ -450,6 +451,14 @@ pub fn walk_path<'v, V: Visitor<'v>>(visitor: &mut V, path: &'v Path) {
     }
 }
 
+pub fn walk_qpath<'v, V: Visitor<'v>>(visitor: &mut V,
+                                      qpath_span: Span,
+                                      qpath: &'v QPath) {
+    visitor.visit_ty(&*qpath.self_type);
+    visitor.visit_trait_ref(&*qpath.trait_ref);
+    visitor.visit_path_segment(qpath_span, &qpath.item_path);
+}
+
 pub fn walk_path_segment<'v, V: Visitor<'v>>(visitor: &mut V,
                                              path_span: Span,
                                              segment: &'v PathSegment) {
@@ -881,6 +890,9 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
         ExprPath(ref path) => {
             visitor.visit_path(path, expression.id)
         }
+        ExprQPath(ref qpath) => {
+            visitor.visit_qpath(expression.span, &**qpath)
+        }
         ExprBreak(_) | ExprAgain(_) => {}
         ExprRet(ref optional_expression) => {
             walk_expr_opt(visitor, optional_expression)