rollup merge of #19298: nikomatsakis/unboxed-closure-parse-the-plus

Implements RFC 438.

Fixes #19092.

This is a [breaking-change]: change types like `&Foo+Send` or `&'a mut Foo+'a` to `&(Foo+Send)` and `&'a mut (Foo+'a)`, respectively.

r? @brson

13 files changed, 146 insertions, 166 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 3d33774aa55..14f164ff23b 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1151,7 +1151,9 @@ pub enum Ty_ {
     /// A path (`module::module::...::Type`) or primitive
     ///
     /// Type parameters are stored in the Path itself
-    TyPath(Path, Option<TyParamBounds>, NodeId), // for #7264; see above
+    TyPath(Path, NodeId),
+    /// Something like `A+B`. Note that `B` must always be a path.
+    TyObjectSum(P<Ty>, TyParamBounds),
     /// A type like `for<'a> Foo<&'a Bar>`
     TyPolyTraitRef(TyParamBounds),
     /// A "qualified path", e.g. `<Vec<T> as SomeTrait>::SomeType`
diff --git a/src/libsyntax/ast_util.rs b/src/libsyntax/ast_util.rs
index 043e79bffd9..4d6ac4f3430 100644
--- a/src/libsyntax/ast_util.rs
+++ b/src/libsyntax/ast_util.rs
@@ -454,7 +454,7 @@ impl<'a, 'v, O: IdVisitingOperation> Visitor<'v> for IdVisitor<'a, O> {
     fn visit_ty(&mut self, typ: &Ty) {
         self.operation.visit_id(typ.id);
         match typ.node {
-            TyPath(_, _, id) => self.operation.visit_id(id),
+            TyPath(_, id) => self.operation.visit_id(id),
             _ => {}
         }
         visit::walk_ty(self, typ)
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 2c7f9e889f8..bd01e5e6430 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -44,7 +44,8 @@ pub trait AstBuilder {
     fn ty_mt(&self, ty: P<ast::Ty>, mutbl: ast::Mutability) -> ast::MutTy;
 
     fn ty(&self, span: Span, ty: ast::Ty_) -> P<ast::Ty>;
-    fn ty_path(&self, ast::Path, Option<OwnedSlice<ast::TyParamBound>>) -> P<ast::Ty>;
+    fn ty_path(&self, ast::Path) -> P<ast::Ty>;
+    fn ty_sum(&self, ast::Path, OwnedSlice<ast::TyParamBound>) -> P<ast::Ty>;
     fn ty_ident(&self, span: Span, idents: ast::Ident) -> P<ast::Ty>;
 
     fn ty_rptr(&self, span: Span,
@@ -344,17 +345,21 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         })
     }
 
-    fn ty_path(&self, path: ast::Path, bounds: Option<OwnedSlice<ast::TyParamBound>>)
-              -> P<ast::Ty> {
+    fn ty_path(&self, path: ast::Path) -> P<ast::Ty> {
+        self.ty(path.span, ast::TyPath(path, ast::DUMMY_NODE_ID))
+    }
+
+    fn ty_sum(&self, path: ast::Path, bounds: OwnedSlice<ast::TyParamBound>) -> P<ast::Ty> {
         self.ty(path.span,
-                ast::TyPath(path, bounds, ast::DUMMY_NODE_ID))
+                ast::TyObjectSum(self.ty_path(path),
+                                 bounds))
     }
 
     // Might need to take bounds as an argument in the future, if you ever want
     // to generate a bounded existential trait type.
     fn ty_ident(&self, span: Span, ident: ast::Ident)
         -> P<ast::Ty> {
-        self.ty_path(self.path_ident(span, ident), None)
+        self.ty_path(self.path_ident(span, ident))
     }
 
     fn ty_rptr(&self,
@@ -386,7 +391,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
                               self.ident_of("Option")
                           ),
                           Vec::new(),
-                          vec!( ty )), None)
+                          vec!( ty )))
     }
 
     fn ty_field_imm(&self, span: Span, name: Ident, ty: P<ast::Ty>) -> ast::TypeField {
@@ -425,8 +430,10 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
     }
 
     fn ty_vars_global(&self, ty_params: &OwnedSlice<ast::TyParam>) -> Vec<P<ast::Ty>> {
-        ty_params.iter().map(|p| self.ty_path(
-                self.path_global(DUMMY_SP, vec!(p.ident)), None)).collect()
+        ty_params
+            .iter()
+            .map(|p| self.ty_path(self.path_global(DUMMY_SP, vec!(p.ident))))
+            .collect()
     }
 
     fn trait_ref(&self, path: ast::Path) -> ast::TraitRef {
diff --git a/src/libsyntax/ext/deriving/generic/mod.rs b/src/libsyntax/ext/deriving/generic/mod.rs
index fcd4966683d..d5f472bd827 100644
--- a/src/libsyntax/ext/deriving/generic/mod.rs
+++ b/src/libsyntax/ext/deriving/generic/mod.rs
@@ -444,7 +444,7 @@ impl<'a> TraitDef<'a> {
         // Create the type of `self`.
         let self_type = cx.ty_path(
             cx.path_all(self.span, false, vec!( type_ident ), self_lifetimes,
-                        self_ty_params.into_vec()), None);
+                        self_ty_params.into_vec()));
 
         let attr = cx.attribute(
             self.span,
diff --git a/src/libsyntax/ext/deriving/generic/ty.rs b/src/libsyntax/ext/deriving/generic/ty.rs
index 700ada8b4ad..6614ab50f1e 100644
--- a/src/libsyntax/ext/deriving/generic/ty.rs
+++ b/src/libsyntax/ext/deriving/generic/ty.rs
@@ -70,7 +70,7 @@ impl<'a> Path<'a> {
                  self_ty: Ident,
                  self_generics: &Generics)
                  -> P<ast::Ty> {
-        cx.ty_path(self.to_path(cx, span, self_ty, self_generics), None)
+        cx.ty_path(self.to_path(cx, span, self_ty, self_generics))
     }
     pub fn to_path(&self,
                    cx: &ExtCtxt,
@@ -152,7 +152,7 @@ impl<'a> Ty<'a> {
             }
             Literal(ref p) => { p.to_ty(cx, span, self_ty, self_generics) }
             Self  => {
-                cx.ty_path(self.to_path(cx, span, self_ty, self_generics), None)
+                cx.ty_path(self.to_path(cx, span, self_ty, self_generics))
             }
             Tuple(ref fields) => {
                 let ty = ast::TyTup(fields.iter()
diff --git a/src/libsyntax/ext/format.rs b/src/libsyntax/ext/format.rs
index 490246f8246..d7d6c636849 100644
--- a/src/libsyntax/ext/format.rs
+++ b/src/libsyntax/ext/format.rs
@@ -531,7 +531,7 @@ impl<'a, 'b> Context<'a, 'b> {
                     true, Context::rtpath(self.ecx, "Argument"),
                     vec![static_lifetime],
                     vec![]
-                ), None);
+                ));
             lets.push(Context::item_static_array(self.ecx,
                                                  static_args_name,
                                                  piece_ty,
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index b4cd9779ae2..4785fe37293 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -514,7 +514,7 @@ pub fn parse_nt(p: &mut Parser, name: &str) -> Nonterminal {
       "stmt" => token::NtStmt(p.parse_stmt(Vec::new())),
       "pat" => token::NtPat(p.parse_pat()),
       "expr" => token::NtExpr(p.parse_expr()),
-      "ty" => token::NtTy(p.parse_ty(false /* no need to disambiguate*/)),
+      "ty" => token::NtTy(p.parse_ty()),
       // this could be handled like a token, since it is one
       "ident" => match p.token {
         token::Ident(sn,b) => { p.bump(); token::NtIdent(box sn,b) }
@@ -525,7 +525,7 @@ pub fn parse_nt(p: &mut Parser, name: &str) -> Nonterminal {
         }
       },
       "path" => {
-        token::NtPath(box p.parse_path(LifetimeAndTypesWithoutColons).path)
+        token::NtPath(box p.parse_path(LifetimeAndTypesWithoutColons))
       }
       "meta" => token::NtMeta(p.parse_meta_item()),
       "tt" => {
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 6941c0e9c18..122f99cabb3 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -433,11 +433,13 @@ pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
             }
             TyTup(tys) => TyTup(tys.move_map(|ty| fld.fold_ty(ty))),
             TyParen(ty) => TyParen(fld.fold_ty(ty)),
-            TyPath(path, bounds, id) => {
+            TyPath(path, id) => {
                 let id = fld.new_id(id);
-                TyPath(fld.fold_path(path),
-                        fld.fold_opt_bounds(bounds),
-                        id)
+                TyPath(fld.fold_path(path), id)
+            }
+            TyObjectSum(ty, bounds) => {
+                TyObjectSum(fld.fold_ty(ty),
+                            fld.fold_bounds(bounds))
             }
             TyQPath(qpath) => {
                 TyQPath(fld.fold_qpath(qpath))
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 96659031e6a..b46f7cdfe22 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -1029,7 +1029,7 @@ mod test {
                                                 parameters: ast::PathParameters::none(),
                                             }
                                         ),
-                                        }, None, ast::DUMMY_NODE_ID),
+                                        }, ast::DUMMY_NODE_ID),
                                         span:sp(10,13)
                                     }),
                                     pat: P(ast::Pat {
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index c731a0005f8..35187ebb522 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -111,16 +111,6 @@ pub enum PathParsingMode {
     /// A path with a lifetime and type parameters with double colons before
     /// the type parameters; e.g. `foo::bar::<'a>::Baz::<T>`
     LifetimeAndTypesWithColons,
-    /// A path with a lifetime and type parameters with bounds before the last
-    /// set of type parameters only; e.g. `foo::bar<'a>::Baz+X+Y<T>` This
-    /// form does not use extra double colons.
-    LifetimeAndTypesAndBounds,
-}
-
-/// A path paired with optional type bounds.
-pub struct PathAndBounds {
-    pub path: ast::Path,
-    pub bounds: Option<ast::TyParamBounds>,
 }
 
 enum ItemOrViewItem {
@@ -1053,17 +1043,9 @@ impl<'a> Parser<'a> {
         }
     }
 
-    pub fn parse_ty_path(&mut self, plus_allowed: bool) -> Ty_ {
-        let mode = if plus_allowed {
-            LifetimeAndTypesAndBounds
-        } else {
-            LifetimeAndTypesWithoutColons
-        };
-        let PathAndBounds {
-            path,
-            bounds
-        } = self.parse_path(mode);
-        TyPath(path, bounds, ast::DUMMY_NODE_ID)
+    pub fn parse_ty_path(&mut self) -> Ty_ {
+        let path = self.parse_path(LifetimeAndTypesWithoutColons);
+        TyPath(path, ast::DUMMY_NODE_ID)
     }
 
     /// parse a TyBareFn type:
@@ -1286,7 +1268,7 @@ impl<'a> Parser<'a> {
         let lo = self.span.lo;
         let ident = self.parse_ident();
         self.expect(&token::Eq);
-        let typ = self.parse_ty(true);
+        let typ = self.parse_ty_sum();
         let hi = self.span.hi;
         self.expect(&token::Semi);
         Typedef {
@@ -1385,7 +1367,7 @@ impl<'a> Parser<'a> {
     /// Parse a possibly mutable type
     pub fn parse_mt(&mut self) -> MutTy {
         let mutbl = self.parse_mutability();
-        let t = self.parse_ty(true);
+        let t = self.parse_ty();
         MutTy { ty: t, mutbl: mutbl }
     }
 
@@ -1396,7 +1378,7 @@ impl<'a> Parser<'a> {
         let mutbl = self.parse_mutability();
         let id = self.parse_ident();
         self.expect(&token::Colon);
-        let ty = self.parse_ty(true);
+        let ty = self.parse_ty_sum();
         let hi = ty.span.hi;
         ast::TypeField {
             ident: id,
@@ -1411,7 +1393,19 @@ impl<'a> Parser<'a> {
             if self.eat(&token::Not) {
                 NoReturn(self.span)
             } else {
-                Return(self.parse_ty(true))
+                let t = self.parse_ty();
+
+                // We used to allow `fn foo() -> &T + U`, but don't
+                // anymore. If we see it, report a useful error.  This
+                // only makes sense because `parse_ret_ty` is only
+                // used in fn *declarations*, not fn types or where
+                // clauses (i.e., not when parsing something like
+                // `FnMut() -> T + Send`, where the `+` is legal).
+                if self.token == token::BinOp(token::Plus) {
+                    self.warn("deprecated syntax: `()` are required, see RFC 248 for details");
+                }
+
+                Return(t)
             }
         } else {
             let pos = self.span.lo;
@@ -1423,11 +1417,36 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Parse a type in a context where `T1+T2` is allowed.
+    pub fn parse_ty_sum(&mut self) -> P<Ty> {
+        let lo = self.span.lo;
+        let lhs = self.parse_ty();
+
+        if !self.eat(&token::BinOp(token::Plus)) {
+            return lhs;
+        }
+
+        let bounds = self.parse_ty_param_bounds();
+
+        // In type grammar, `+` is treated like a binary operator,
+        // and hence both L and R side are required.
+        if bounds.len() == 0 {
+            let last_span = self.last_span;
+            self.span_err(last_span,
+                          "at least one type parameter bound \
+                          must be specified");
+        }
+
+        let sp = mk_sp(lo, self.last_span.hi);
+        let sum = ast::TyObjectSum(lhs, bounds);
+        P(Ty {id: ast::DUMMY_NODE_ID, node: sum, span: sp})
+    }
+
     /// Parse a type.
     ///
     /// The second parameter specifies whether the `+` binary operator is
     /// allowed in the type grammar.
-    pub fn parse_ty(&mut self, plus_allowed: bool) -> P<Ty> {
+    pub fn parse_ty(&mut self) -> P<Ty> {
         maybe_whole!(no_clone self, NtTy);
 
         let lo = self.span.lo;
@@ -1441,7 +1460,7 @@ impl<'a> Parser<'a> {
             let mut ts = vec![];
             let mut last_comma = false;
             while self.token != token::CloseDelim(token::Paren) {
-                ts.push(self.parse_ty(true));
+                ts.push(self.parse_ty_sum());
                 if self.token == token::Comma {
                     last_comma = true;
                     self.bump();
@@ -1465,7 +1484,7 @@ impl<'a> Parser<'a> {
                 token::OpenDelim(token::Bracket) => self.obsolete(last_span, ObsoleteOwnedVector),
                 _ => self.obsolete(last_span, ObsoleteOwnedType)
             }
-            TyTup(vec![self.parse_ty(false)])
+            TyTup(vec![self.parse_ty()])
         } else if self.token == token::BinOp(token::Star) {
             // STAR POINTER (bare pointer?)
             self.bump();
@@ -1473,7 +1492,7 @@ impl<'a> Parser<'a> {
         } else if self.token == token::OpenDelim(token::Bracket) {
             // VECTOR
             self.expect(&token::OpenDelim(token::Bracket));
-            let t = self.parse_ty(true);
+            let t = self.parse_ty_sum();
 
             // Parse the `, ..e` in `[ int, ..e ]`
             // where `e` is a const expression
@@ -1514,7 +1533,7 @@ impl<'a> Parser<'a> {
         } else if self.token == token::Lt {
             // QUALIFIED PATH `<TYPE as TRAIT_REF>::item`
             self.bump();
-            let self_type = self.parse_ty(true);
+            let self_type = self.parse_ty_sum();
             self.expect_keyword(keywords::As);
             let trait_ref = self.parse_trait_ref();
             self.expect(&token::Gt);
@@ -1529,7 +1548,7 @@ impl<'a> Parser<'a> {
                   self.token.is_ident() ||
                   self.token.is_path() {
             // NAMED TYPE
-            self.parse_ty_path(plus_allowed)
+            self.parse_ty_path()
         } else if self.eat(&token::Underscore) {
             // TYPE TO BE INFERRED
             TyInfer
@@ -1563,7 +1582,7 @@ impl<'a> Parser<'a> {
                            known as `*const T`");
             MutImmutable
         };
-        let t = self.parse_ty(true);
+        let t = self.parse_ty();
         MutTy { ty: t, mutbl: mutbl }
     }
 
@@ -1603,7 +1622,7 @@ impl<'a> Parser<'a> {
                                    special_idents::invalid)
         };
 
-        let t = self.parse_ty(true);
+        let t = self.parse_ty_sum();
 
         Arg {
             ty: t,
@@ -1621,7 +1640,7 @@ impl<'a> Parser<'a> {
     pub fn parse_fn_block_arg(&mut self) -> Arg {
         let pat = self.parse_pat();
         let t = if self.eat(&token::Colon) {
-            self.parse_ty(true)
+            self.parse_ty_sum()
         } else {
             P(Ty {
                 id: ast::DUMMY_NODE_ID,
@@ -1739,7 +1758,7 @@ impl<'a> Parser<'a> {
     /// mode. The `mode` parameter determines whether lifetimes, types, and/or
     /// bounds are permitted and whether `::` must precede type parameter
     /// groups.
-    pub fn parse_path(&mut self, mode: PathParsingMode) -> PathAndBounds {
+    pub fn parse_path(&mut self, mode: PathParsingMode) -> ast::Path {
         // Check for a whole path...
         let found = match self.token {
             token::Interpolated(token::NtPath(_)) => Some(self.bump_and_get()),
@@ -1747,10 +1766,7 @@ impl<'a> Parser<'a> {
         };
         match found {
             Some(token::Interpolated(token::NtPath(box path))) => {
-                return PathAndBounds {
-                    path: path,
-                    bounds: None
-                }
+                return path;
             }
             _ => {}
         }
@@ -1762,8 +1778,7 @@ impl<'a> Parser<'a> {
         // identifier followed by an optional lifetime and a set of types.
         // A bound set is a set of type parameter bounds.
         let segments = match mode {
-            LifetimeAndTypesWithoutColons |
-            LifetimeAndTypesAndBounds => {
+            LifetimeAndTypesWithoutColons => {
                 self.parse_path_segments_without_colons()
             }
             LifetimeAndTypesWithColons => {
@@ -1774,44 +1789,14 @@ impl<'a> Parser<'a> {
             }
         };
 
-        // Next, parse a plus and bounded type parameters, if
-        // applicable. We need to remember whether the separate was
-        // present for later, because in some contexts it's a parse
-        // error.
-        let opt_bounds = {
-            if mode == LifetimeAndTypesAndBounds &&
-                self.eat(&token::BinOp(token::Plus))
-            {
-                let bounds = self.parse_ty_param_bounds();
-
-                // For some reason that I do not fully understand, we
-                // do not permit an empty list in the case where it is
-                // introduced by a `+`, but we do for `:` and other
-                // separators. -nmatsakis
-                if bounds.len() == 0 {
-                    let last_span = self.last_span;
-                    self.span_err(last_span,
-                                  "at least one type parameter bound \
-                                   must be specified");
-                }
-
-                Some(bounds)
-            } else {
-                None
-            }
-        };
-
         // Assemble the span.
         let span = mk_sp(lo, self.last_span.hi);
 
         // Assemble the result.
-        PathAndBounds {
-            path: ast::Path {
-                span: span,
-                global: is_global,
-                segments: segments,
-            },
-            bounds: opt_bounds,
+        ast::Path {
+            span: span,
+            global: is_global,
+            segments: segments,
         }
     }
 
@@ -1837,10 +1822,10 @@ impl<'a> Parser<'a> {
                 let inputs = self.parse_seq_to_end(
                     &token::CloseDelim(token::Paren),
                     seq_sep_trailing_allowed(token::Comma),
-                    |p| p.parse_ty(true));
+                    |p| p.parse_ty_sum());
 
                 let output_ty = if self.eat(&token::RArrow) {
-                    Some(self.parse_ty(true))
+                    Some(self.parse_ty())
                 } else {
                     None
                 };
@@ -2327,7 +2312,7 @@ impl<'a> Parser<'a> {
                         !self.token.is_keyword(keywords::True) &&
                         !self.token.is_keyword(keywords::False) {
                     let pth =
-                        self.parse_path(LifetimeAndTypesWithColons).path;
+                        self.parse_path(LifetimeAndTypesWithColons);
 
                     // `!`, as an operator, is prefix, so we know this isn't that
                     if self.token == token::Not {
@@ -2898,7 +2883,7 @@ impl<'a> Parser<'a> {
             }
             None => {
                 if as_prec > min_prec && self.eat_keyword(keywords::As) {
-                    let rhs = self.parse_ty(false);
+                    let rhs = self.parse_ty();
                     let _as = self.mk_expr(lhs.span.lo,
                                            rhs.span.hi,
                                            ExprCast(lhs, rhs));
@@ -3362,8 +3347,7 @@ impl<'a> Parser<'a> {
                     }) {
                 self.bump();
                 let end = if self.token.is_ident() || self.token.is_path() {
-                    let path = self.parse_path(LifetimeAndTypesWithColons)
-                                   .path;
+                    let path = self.parse_path(LifetimeAndTypesWithColons);
                     let hi = self.span.hi;
                     self.mk_expr(lo, hi, ExprPath(path))
                 } else {
@@ -3433,8 +3417,7 @@ impl<'a> Parser<'a> {
                 }
             } else {
                 // parse an enum pat
-                let enum_path = self.parse_path(LifetimeAndTypesWithColons)
-                                    .path;
+                let enum_path = self.parse_path(LifetimeAndTypesWithColons);
                 match self.token {
                     token::OpenDelim(token::Brace) => {
                         self.bump();
@@ -3548,7 +3531,7 @@ impl<'a> Parser<'a> {
             span: mk_sp(lo, lo),
         });
         if self.eat(&token::Colon) {
-            ty = self.parse_ty(true);
+            ty = self.parse_ty_sum();
         }
         let init = self.parse_initializer();
         P(ast::Local {
@@ -3577,7 +3560,7 @@ impl<'a> Parser<'a> {
         }
         let name = self.parse_ident();
         self.expect(&token::Colon);
-        let ty = self.parse_ty(true);
+        let ty = self.parse_ty_sum();
         spanned(lo, self.last_span.hi, ast::StructField_ {
             kind: NamedField(name, pr),
             id: ast::DUMMY_NODE_ID,
@@ -3624,7 +3607,7 @@ impl<'a> Parser<'a> {
 
             // Potential trouble: if we allow macros with paths instead of
             // idents, we'd need to look ahead past the whole path here...
-            let pth = self.parse_path(NoTypesAllowed).path;
+            let pth = self.parse_path(NoTypesAllowed);
             self.bump();
 
             let id = match self.token {
@@ -3976,7 +3959,7 @@ impl<'a> Parser<'a> {
 
         let default = if self.token == token::Eq {
             self.bump();
-            Some(self.parse_ty(true))
+            Some(self.parse_ty_sum())
         }
         else { None };
 
@@ -4032,7 +4015,7 @@ impl<'a> Parser<'a> {
             Some(token::Comma),
             |p| {
                 p.forbid_lifetime();
-                p.parse_ty(true)
+                p.parse_ty_sum()
             }
         );
         (lifetimes, result.into_vec())
@@ -4265,7 +4248,7 @@ impl<'a> Parser<'a> {
                     // Determine whether this is the fully explicit form, `self:
                     // TYPE`.
                     if self.eat(&token::Colon) {
-                        SelfExplicit(self.parse_ty(false), self_ident)
+                        SelfExplicit(self.parse_ty_sum(), self_ident)
                     } else {
                         SelfValue(self_ident)
                     }
@@ -4277,7 +4260,7 @@ impl<'a> Parser<'a> {
                     // Determine whether this is the fully explicit form,
                     // `self: TYPE`.
                     if self.eat(&token::Colon) {
-                        SelfExplicit(self.parse_ty(false), self_ident)
+                        SelfExplicit(self.parse_ty_sum(), self_ident)
                     } else {
                         SelfValue(self_ident)
                     }
@@ -4466,7 +4449,7 @@ impl<'a> Parser<'a> {
                 && (self.look_ahead(2, |t| *t == token::OpenDelim(token::Paren))
                     || self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))) {
                 // method macro.
-                let pth = self.parse_path(NoTypesAllowed).path;
+                let pth = self.parse_path(NoTypesAllowed);
                 self.expect(&token::Not);
 
                 // eat a matched-delimiter token tree:
@@ -4564,30 +4547,25 @@ impl<'a> Parser<'a> {
         let could_be_trait = self.token != token::OpenDelim(token::Paren);
 
         // Parse the trait.
-        let mut ty = self.parse_ty(true);
+        let mut ty = self.parse_ty_sum();
 
         // Parse traits, if necessary.
         let opt_trait = if could_be_trait && self.eat_keyword(keywords::For) {
             // New-style trait. Reinterpret the type as a trait.
             let opt_trait_ref = match ty.node {
-                TyPath(ref path, None, node_id) => {
+                TyPath(ref path, node_id) => {
                     Some(TraitRef {
                         path: (*path).clone(),
                         ref_id: node_id,
                     })
                 }
-                TyPath(_, Some(_), _) => {
-                    self.span_err(ty.span,
-                                  "bounded traits are only valid in type position");
-                    None
-                }
                 _ => {
                     self.span_err(ty.span, "not a trait");
                     None
                 }
             };
 
-            ty = self.parse_ty(true);
+            ty = self.parse_ty_sum();
             opt_trait_ref
         } else {
             None
@@ -4606,7 +4584,7 @@ impl<'a> Parser<'a> {
     /// Parse a::B<String,int>
     fn parse_trait_ref(&mut self) -> TraitRef {
         ast::TraitRef {
-            path: self.parse_path(LifetimeAndTypesWithoutColons).path,
+            path: self.parse_path(LifetimeAndTypesWithoutColons),
             ref_id: ast::DUMMY_NODE_ID,
         }
     }
@@ -4638,7 +4616,7 @@ impl<'a> Parser<'a> {
         let mut generics = self.parse_generics();
 
         if self.eat(&token::Colon) {
-            let ty = self.parse_ty(true);
+            let ty = self.parse_ty_sum();
             self.span_err(ty.span, "`virtual` structs have been removed from the language");
         }
 
@@ -4673,7 +4651,7 @@ impl<'a> Parser<'a> {
                 let struct_field_ = ast::StructField_ {
                     kind: UnnamedField(p.parse_visibility()),
                     id: ast::DUMMY_NODE_ID,
-                    ty: p.parse_ty(true),
+                    ty: p.parse_ty_sum(),
                     attrs: attrs,
                 };
                 spanned(lo, p.span.hi, struct_field_)
@@ -4830,7 +4808,7 @@ impl<'a> Parser<'a> {
     fn parse_item_const(&mut self, m: Option<Mutability>) -> ItemInfo {
         let id = self.parse_ident();
         self.expect(&token::Colon);
-        let ty = self.parse_ty(true);
+        let ty = self.parse_ty_sum();
         self.expect(&token::Eq);
         let e = self.parse_expr();
         self.commit_expr_expecting(&*e, token::Semi);
@@ -5023,7 +5001,7 @@ impl<'a> Parser<'a> {
 
         let ident = self.parse_ident();
         self.expect(&token::Colon);
-        let ty = self.parse_ty(true);
+        let ty = self.parse_ty_sum();
         let hi = self.span.hi;
         self.expect(&token::Semi);
         P(ForeignItem {
@@ -5181,7 +5159,7 @@ impl<'a> Parser<'a> {
         let mut tps = self.parse_generics();
         self.parse_where_clause(&mut tps);
         self.expect(&token::Eq);
-        let ty = self.parse_ty(true);
+        let ty = self.parse_ty_sum();
         self.expect(&token::Semi);
         (ident, ItemTy(ty, tps), None)
     }
@@ -5235,7 +5213,7 @@ impl<'a> Parser<'a> {
                     &token::OpenDelim(token::Paren),
                     &token::CloseDelim(token::Paren),
                     seq_sep_trailing_allowed(token::Comma),
-                    |p| p.parse_ty(true)
+                    |p| p.parse_ty_sum()
                 );
                 for ty in arg_tys.into_iter() {
                     args.push(ast::VariantArg {
@@ -5593,7 +5571,7 @@ impl<'a> Parser<'a> {
             // MACRO INVOCATION ITEM
 
             // item macro.
-            let pth = self.parse_path(NoTypesAllowed).path;
+            let pth = self.parse_path(NoTypesAllowed);
             self.expect(&token::Not);
 
             // a 'special' identifier (like what `macro_rules!` uses)
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 6960337c3e2..ab78d5ecbfd 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -61,7 +61,7 @@ pub struct State<'a> {
     literals: Option<Vec<comments::Literal> >,
     cur_cmnt_and_lit: CurrentCommentAndLiteral,
     boxes: Vec<pp::Breaks>,
-    ann: &'a PpAnn+'a,
+    ann: &'a (PpAnn+'a),
     encode_idents_with_hygiene: bool,
 }
 
@@ -293,6 +293,10 @@ pub fn ty_to_string(ty: &ast::Ty) -> String {
     $to_string(|s| s.print_type(ty))
 }
 
+pub fn bounds_to_string(bounds: &[ast::TyParamBound]) -> String {
+    $to_string(|s| s.print_bounds("", bounds))
+}
+
 pub fn pat_to_string(pat: &ast::Pat) -> String {
     $to_string(|s| s.print_pat(pat))
 }
@@ -739,11 +743,15 @@ impl<'a> State<'a> {
                                       Some(&generics),
                                       None));
             }
-            ast::TyPath(ref path, ref bounds, _) => {
-                try!(self.print_bounded_path(path, bounds));
+            ast::TyPath(ref path, _) => {
+                try!(self.print_path(path, false));
+            }
+            ast::TyObjectSum(ref ty, ref bounds) => {
+                try!(self.print_type(&**ty));
+                try!(self.print_bounds("+", bounds.as_slice()));
             }
             ast::TyPolyTraitRef(ref bounds) => {
-                try!(self.print_bounds("", bounds));
+                try!(self.print_bounds("", bounds.as_slice()));
             }
             ast::TyQPath(ref qpath) => {
                 try!(word(&mut self.s, "<"));
@@ -970,7 +978,7 @@ impl<'a> State<'a> {
                     }
                     _ => {}
                 }
-                try!(self.print_bounds(":", bounds));
+                try!(self.print_bounds(":", bounds.as_slice()));
                 try!(self.print_where_clause(generics));
                 try!(word(&mut self.s, " "));
                 try!(self.bopen());
@@ -1908,11 +1916,11 @@ impl<'a> State<'a> {
         self.print_expr(coll)
     }
 
-    fn print_path_(&mut self,
-                   path: &ast::Path,
-                   colons_before_params: bool,
-                   opt_bounds: &Option<OwnedSlice<ast::TyParamBound>>)
-        -> IoResult<()> {
+    fn print_path(&mut self,
+                  path: &ast::Path,
+                  colons_before_params: bool)
+                  -> IoResult<()>
+    {
         try!(self.maybe_print_comment(path.span.lo));
         if path.global {
             try!(word(&mut self.s, "::"));
@@ -1931,10 +1939,7 @@ impl<'a> State<'a> {
             try!(self.print_path_parameters(&segment.parameters, colons_before_params));
         }
 
-        match *opt_bounds {
-            None => Ok(()),
-            Some(ref bounds) => self.print_bounds("+", bounds)
-        }
+        Ok(())
     }
 
     fn print_path_parameters(&mut self,
@@ -1997,17 +2002,6 @@ impl<'a> State<'a> {
         Ok(())
     }
 
-    fn print_path(&mut self, path: &ast::Path,
-                  colons_before_params: bool) -> IoResult<()> {
-        self.print_path_(path, colons_before_params, &None)
-    }
-
-    fn print_bounded_path(&mut self, path: &ast::Path,
-                          bounds: &Option<OwnedSlice<ast::TyParamBound>>)
-        -> IoResult<()> {
-        self.print_path_(path, false, bounds)
-    }
-
     pub fn print_pat(&mut self, pat: &ast::Pat) -> IoResult<()> {
         try!(self.maybe_print_comment(pat.span.lo));
         try!(self.ann.pre(self, NodePat(pat)));
@@ -2329,7 +2323,7 @@ impl<'a> State<'a> {
 
     pub fn print_bounds(&mut self,
                         prefix: &str,
-                        bounds: &OwnedSlice<ast::TyParamBound>)
+                        bounds: &[ast::TyParamBound])
                         -> IoResult<()> {
         if !bounds.is_empty() {
             try!(word(&mut self.s, prefix));
@@ -2418,7 +2412,7 @@ impl<'a> State<'a> {
             _ => {}
         }
         try!(self.print_ident(param.ident));
-        try!(self.print_bounds(":", &param.bounds));
+        try!(self.print_bounds(":", param.bounds.as_slice()));
         match param.default {
             Some(ref default) => {
                 try!(space(&mut self.s));
@@ -2447,7 +2441,7 @@ impl<'a> State<'a> {
             }
 
             try!(self.print_ident(predicate.ident));
-            try!(self.print_bounds(":", &predicate.bounds));
+            try!(self.print_bounds(":", predicate.bounds.as_slice()));
         }
 
         Ok(())
@@ -2664,7 +2658,7 @@ impl<'a> State<'a> {
             try!(self.pclose());
         }
 
-        try!(self.print_bounds(":", bounds));
+        try!(self.print_bounds(":", bounds.as_slice()));
 
         try!(self.print_fn_output(decl));
 
diff --git a/src/libsyntax/test.rs b/src/libsyntax/test.rs
index f21a3185d6d..05828fc05f8 100644
--- a/src/libsyntax/test.rs
+++ b/src/libsyntax/test.rs
@@ -482,8 +482,7 @@ fn mk_tests(cx: &TestCtxt) -> P<ast::Item> {
     let ecx = &cx.ext_cx;
     let struct_type = ecx.ty_path(ecx.path(sp, vec![ecx.ident_of("self"),
                                                     ecx.ident_of("test"),
-                                                    ecx.ident_of("TestDescAndFn")]),
-                                  None);
+                                                    ecx.ident_of("TestDescAndFn")]));
     let static_lt = ecx.lifetime(sp, token::special_idents::static_lifetime.name);
     // &'static [self::test::TestDescAndFn]
     let static_type = ecx.ty_rptr(sp,
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 3f87dbc0740..95679bc6bf0 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -404,14 +404,12 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty) {
             walk_fn_ret_ty(visitor, &function_declaration.decl.output);
             walk_lifetime_decls_helper(visitor, &function_declaration.lifetimes);
         }
-        TyPath(ref path, ref opt_bounds, id) => {
+        TyPath(ref path, id) => {
             visitor.visit_path(path, id);
-            match *opt_bounds {
-                Some(ref bounds) => {
-                    walk_ty_param_bounds_helper(visitor, bounds);
-                }
-                None => { }
-            }
+        }
+        TyObjectSum(ref ty, ref bounds) => {
+            visitor.visit_ty(&**ty);
+            walk_ty_param_bounds_helper(visitor, bounds);
         }
         TyQPath(ref qpath) => {
             visitor.visit_ty(&*qpath.self_type);