diff --git a/doc/tutorial.md b/doc/tutorial.md
index 648aa24a08f..41895ebed7c 100644
--- a/doc/tutorial.md
+++ b/doc/tutorial.md
@@ -2072,12 +2072,12 @@ on values of type `T` inside the function. It will also cause a
 compile-time error when anyone tries to call `print_all` on an array
 whose element type does not have a `Printable` implementation.
 
-Type parameters can have multiple bounds by separating them with spaces,
+Type parameters can have multiple bounds by separating them with `+`,
 as in this version of `print_all` that copies elements.
 
 ~~~
 # trait Printable { fn print(&self); }
-fn print_all<T: Printable Copy>(printable_things: ~[T]) {
+fn print_all<T: Printable + Copy>(printable_things: ~[T]) {
     let mut i = 0;
     while i < printable_things.len() {
         let copy_of_thing = printable_things[i];
diff --git a/src/libcore/pipes.rs b/src/libcore/pipes.rs
index b3e32fc6b6c..29a947e5890 100644
--- a/src/libcore/pipes.rs
+++ b/src/libcore/pipes.rs
@@ -1213,8 +1213,8 @@ pub trait Select2<T:Owned,U:Owned> {
 
 impl<T: Owned,
      U: Owned,
-     Left: Selectable GenericPort<T>,
-     Right: Selectable GenericPort<U>>
+     Left: Selectable + GenericPort<T>,
+     Right: Selectable + GenericPort<U>>
      Select2<T,U> for (Left, Right) {
     fn select() -> Either<T, U> {
         match self {
diff --git a/src/librustc/middle/typeck/infer/lattice.rs b/src/librustc/middle/typeck/infer/lattice.rs
index 3998967dc98..c7ee1b871a8 100644
--- a/src/librustc/middle/typeck/infer/lattice.rs
+++ b/src/librustc/middle/typeck/infer/lattice.rs
@@ -72,8 +72,8 @@ pub impl LatticeValue for ty::t {
 }
 
 pub impl CombineFields {
-    fn var_sub_var<T:Copy InferStr LatticeValue,
-                   V:Copy Eq ToStr Vid UnifyVid<Bounds<T>>>(
+    fn var_sub_var<T:Copy + InferStr + LatticeValue,
+                   V:Copy + Eq + ToStr + Vid + UnifyVid<Bounds<T>>>(
         &self,
         +a_id: V,
         +b_id: V) -> ures
@@ -125,8 +125,8 @@ pub impl CombineFields {
     }
 
     /// make variable a subtype of T
-    fn var_sub_t<T:Copy InferStr LatticeValue,
-                 V:Copy Eq ToStr Vid UnifyVid<Bounds<T>>>(
+    fn var_sub_t<T:Copy + InferStr + LatticeValue,
+                 V:Copy + Eq + ToStr + Vid + UnifyVid<Bounds<T>>>(
         &self,
         +a_id: V,
         +b: T) -> ures
@@ -149,8 +149,8 @@ pub impl CombineFields {
             a_id, a_bounds, b_bounds, node_a.rank)
     }
 
-    fn t_sub_var<T:Copy InferStr LatticeValue,
-                 V:Copy Eq ToStr Vid UnifyVid<Bounds<T>>>(
+    fn t_sub_var<T:Copy + InferStr + LatticeValue,
+                 V:Copy + Eq + ToStr + Vid + UnifyVid<Bounds<T>>>(
         &self,
         +a: T,
         +b_id: V) -> ures
@@ -201,8 +201,8 @@ pub impl CombineFields {
         }
     }
 
-    fn set_var_to_merged_bounds<T:Copy InferStr LatticeValue,
-                                V:Copy Eq ToStr Vid UnifyVid<Bounds<T>>>(
+    fn set_var_to_merged_bounds<T:Copy + InferStr + LatticeValue,
+                                V:Copy+Eq+ToStr+Vid+UnifyVid<Bounds<T>>>(
         &self,
         +v_id: V,
         a: &Bounds<T>,
@@ -395,9 +395,9 @@ pub enum LatticeVarResult<V,T> {
  *   the variables and return the unified variable, in which case the
  *   result is a variable.  This is indicated with a `VarResult`
  *   return. */
-pub fn lattice_vars<L:LatticeDir Combine,
-                    T:Copy InferStr LatticeValue,
-                    V:Copy Eq ToStr Vid UnifyVid<Bounds<T>>>(
+pub fn lattice_vars<L:LatticeDir + Combine,
+                    T:Copy + InferStr + LatticeValue,
+                    V:Copy + Eq + ToStr + Vid + UnifyVid<Bounds<T>>>(
     self: &L,                           // defines whether we want LUB or GLB
     +a_vid: V,                          // first variable
     +b_vid: V,                          // second variable
@@ -441,9 +441,9 @@ pub fn lattice_vars<L:LatticeDir Combine,
     }
 }
 
-pub fn lattice_var_and_t<L:LatticeDir Combine,
-                         T:Copy InferStr LatticeValue,
-                         V:Copy Eq ToStr Vid UnifyVid<Bounds<T>>>(
+pub fn lattice_var_and_t<L:LatticeDir + Combine,
+                         T:Copy + InferStr + LatticeValue,
+                         V:Copy + Eq + ToStr + Vid + UnifyVid<Bounds<T>>>(
     self: &L,
     +a_id: V,
     b: &T,
diff --git a/src/librustc/middle/typeck/infer/unify.rs b/src/librustc/middle/typeck/infer/unify.rs
index 6abf2e5709b..4f85718ad1e 100644
--- a/src/librustc/middle/typeck/infer/unify.rs
+++ b/src/librustc/middle/typeck/infer/unify.rs
@@ -163,8 +163,8 @@ pub fn mk_err<T:SimplyUnifiable>(+a_is_expected: bool,
 }
 
 pub impl InferCtxt {
-    fn simple_vars<T:Copy Eq InferStr SimplyUnifiable,
-                   V:Copy Eq Vid ToStr UnifyVid<Option<T>>>(
+    fn simple_vars<T:Copy + Eq + InferStr + SimplyUnifiable,
+                   V:Copy + Eq + Vid + ToStr + UnifyVid<Option<T>>>(
             &mut self,
             +a_is_expected: bool,
             +a_id: V,
@@ -201,8 +201,8 @@ pub impl InferCtxt {
         return uok();
     }
 
-    fn simple_var_t<T:Copy Eq InferStr SimplyUnifiable,
-                    V:Copy Eq Vid ToStr UnifyVid<Option<T>>>(
+    fn simple_var_t<T:Copy + Eq + InferStr + SimplyUnifiable,
+                    V:Copy + Eq + Vid + ToStr + UnifyVid<Option<T>>>(
             &mut self,
             +a_is_expected: bool,
             +a_id: V,
diff --git a/src/libstd/flatpipes.rs b/src/libstd/flatpipes.rs
index f97e5ee6800..80f93323a8e 100644
--- a/src/libstd/flatpipes.rs
+++ b/src/libstd/flatpipes.rs
@@ -151,7 +151,7 @@ pub mod serial {
     }
 
     /// Create a pair of `FlatChan` and `FlatPort`, backed by pipes
-    pub fn pipe_stream<T: Encodable<DefaultEncoder>
+    pub fn pipe_stream<T: Encodable<DefaultEncoder> +
                           Decodable<DefaultDecoder>>(
                           ) -> (PipePort<T>, PipeChan<T>) {
         let (port, chan) = pipes::stream();
@@ -443,8 +443,8 @@ pub mod flatteners {
     SerializingFlattener
     */
 
-    pub fn deserialize_buffer<D: Decoder FromReader,
-                          T: Decodable<D>>(buf: &[u8]) -> T {
+    pub fn deserialize_buffer<D: Decoder + FromReader,
+                              T: Decodable<D>>(buf: &[u8]) -> T {
         let buf = vec::from_slice(buf);
         let buf_reader = @BufReader::new(buf);
         let reader = buf_reader as @Reader;
@@ -452,8 +452,8 @@ pub mod flatteners {
         Decodable::decode(&deser)
     }
 
-    pub fn serialize_value<D: Encoder FromWriter,
-                       T: Encodable<D>>(val: &T) -> ~[u8] {
+    pub fn serialize_value<D: Encoder + FromWriter,
+                           T: Encodable<D>>(val: &T) -> ~[u8] {
         let bytes_writer = @BytesWriter();
         let writer = bytes_writer as @Writer;
         let ser = FromWriter::from_writer(writer);
diff --git a/src/libstd/workcache.rs b/src/libstd/workcache.rs
index 4de7c1b9925..a06dee723c8 100644
--- a/src/libstd/workcache.rs
+++ b/src/libstd/workcache.rs
@@ -260,9 +260,7 @@ impl Context {
         Context{db: db, logger: lg, cfg: cfg, freshness: LinearMap::new()}
     }
 
-    fn prep<T:Owned
-              Encodable<json::Encoder>
-              Decodable<json::Decoder>>(
+    fn prep<T:Owned + Encodable<json::Encoder> + Decodable<json::Decoder>>(
                   @self,
                   fn_name:&str,
                   blk: fn(@Mut<Prep>)->Work<T>) -> Work<T> {
@@ -278,9 +276,8 @@ trait TPrep {
     fn declare_input(&self, kind:&str, name:&str, val:&str);
     fn is_fresh(&self, cat:&str, kind:&str, name:&str, val:&str) -> bool;
     fn all_fresh(&self, cat:&str, map:&WorkMap) -> bool;
-    fn exec<T:Owned
-        Encodable<json::Encoder>
-        Decodable<json::Decoder>>(&self, blk: ~fn(&Exec) -> T) -> Work<T>;
+    fn exec<T:Owned + Encodable<json::Encoder> + Decodable<json::Decoder>>(
+        &self, blk: ~fn(&Exec) -> T) -> Work<T>;
 }
 
 impl TPrep for @Mut<Prep> {
@@ -318,11 +315,8 @@ impl TPrep for @Mut<Prep> {
         return true;
     }
 
-    fn exec<T:Owned
-        Encodable<json::Encoder>
-        Decodable<json::Decoder>>(&self,
-                                  blk: ~fn(&Exec) -> T) -> Work<T> {
-
+    fn exec<T:Owned + Encodable<json::Encoder> + Decodable<json::Decoder>>(
+            &self, blk: ~fn(&Exec) -> T) -> Work<T> {
         let mut bo = Some(blk);
 
         do self.borrow_imm |p| {
@@ -360,20 +354,15 @@ impl TPrep for @Mut<Prep> {
     }
 }
 
-impl<T:Owned
-       Encodable<json::Encoder>
-       Decodable<json::Decoder>>
-    Work<T> {
+impl<T:Owned + Encodable<json::Encoder> + Decodable<json::Decoder>> Work<T> {
     static fn new(p: @Mut<Prep>, e: Either<T,PortOne<(Exec,T)>>) -> Work<T> {
         Work { prep: p, res: Some(e) }
     }
 }
 
 // FIXME (#3724): movable self. This should be in impl Work.
-fn unwrap<T:Owned
-            Encodable<json::Encoder>
-            Decodable<json::Decoder>>(w: Work<T>) -> T {
-
+fn unwrap<T:Owned + Encodable<json::Encoder> + Decodable<json::Decoder>>(
+        w: Work<T>) -> T {
     let mut ww = w;
     let mut s = None;
 
@@ -383,7 +372,6 @@ fn unwrap<T:Owned
         None => fail!(),
         Some(Left(v)) => v,
         Some(Right(port)) => {
-
             let (exe, v) = match recv(port) {
                 oneshot::send(data) => data
             };
diff --git a/src/libsyntax/parse/obsolete.rs b/src/libsyntax/parse/obsolete.rs
index bf04996838c..f5ee5bd8029 100644
--- a/src/libsyntax/parse/obsolete.rs
+++ b/src/libsyntax/parse/obsolete.rs
@@ -46,7 +46,8 @@ pub enum ObsoleteSyntax {
     ObsoleteBinaryMove,
     ObsoleteUnsafeBlock,
     ObsoleteUnenforcedBound,
-    ObsoleteImplSyntax
+    ObsoleteImplSyntax,
+    ObsoleteTraitBoundSeparator,
 }
 
 pub impl to_bytes::IterBytes for ObsoleteSyntax {
@@ -120,7 +121,11 @@ pub impl Parser {
             ObsoleteImplSyntax => (
                 "colon-separated impl syntax",
                 "write `impl Trait for Type`"
-            )
+            ),
+            ObsoleteTraitBoundSeparator => (
+                "space-separated trait bounds",
+                "write `+` between trait bounds"
+            ),
         };
 
         self.report(sp, kind, kind_str, desc);
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 644d6ed5189..85b4eae25d3 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -75,6 +75,7 @@ use parse::obsolete::{ObsoleteMoveInit, ObsoleteBinaryMove};
 use parse::obsolete::{ObsoleteStructCtor, ObsoleteWith};
 use parse::obsolete::{ObsoleteSyntax, ObsoleteLowerCaseKindBounds};
 use parse::obsolete::{ObsoleteUnsafeBlock, ObsoleteImplSyntax};
+use parse::obsolete::{ObsoleteTraitBoundSeparator};
 use parse::prec::{as_prec, token_to_binop};
 use parse::token::{can_begin_expr, is_ident, is_ident_or_path};
 use parse::token::{is_plain_ident, INTERPOLATED, special_idents};
@@ -2676,7 +2677,12 @@ pub impl Parser {
                 }
 
                 if self.eat(token::BINOP(token::PLUS)) {
-                    // Should be `break;` but that isn't backwards compatible.
+                    loop;
+                }
+
+                if is_ident_or_path(self.token) {
+                    self.obsolete(copy self.span,
+                                  ObsoleteTraitBoundSeparator);
                 }
             }
         }
diff --git a/src/test/run-pass/auto-encode.rs b/src/test/run-pass/auto-encode.rs
index 6bf5293913f..e4004c6dc22 100644
--- a/src/test/run-pass/auto-encode.rs
+++ b/src/test/run-pass/auto-encode.rs
@@ -38,8 +38,8 @@ fn test_prettyprint<A:Encodable<prettyprint::Serializer>>(
 }
 
 fn test_ebml<A:
-    Eq
-    Encodable<EBWriter::Encoder>
+    Eq +
+    Encodable<EBWriter::Encoder> +
     Decodable<EBReader::Decoder>
 >(a1: &A) {
     let bytes = do io::with_bytes_writer |wr| {
diff --git a/src/test/run-pass/issue-2904.rs b/src/test/run-pass/issue-2904.rs
index 9a726bedbc3..9106d39c592 100644
--- a/src/test/run-pass/issue-2904.rs
+++ b/src/test/run-pass/issue-2904.rs
@@ -59,7 +59,7 @@ fn square_from_char(c: char) -> square {
     }
 }
 
-fn read_board_grid<rdr: &static io::Reader>(+in: rdr) -> ~[~[square]] {
+fn read_board_grid<rdr: &static + io::Reader>(+in: rdr) -> ~[~[square]] {
     let in = (in) as io::Reader;
     let mut grid = ~[];
     for in.each_line |line| {