libsyntax: Stop parsing + with no bounds after it.

This will break code that looks like `Box<Trait+>`. Change that code to
`Box<Trait>` instead.

Closes #14925.

[breaking-change]

src/libsyntax/parse/parser.rs

@@ -1646,6 +1646,12 @@ impl<'a> Parser<'a> {
             let bounds = {
                 if self.eat(&token::BINOP(token::PLUS)) {
                     let (_, bounds) = self.parse_ty_param_bounds(false);
+                    if bounds.len() == 0 {
+                        let last_span = self.last_span;
+                        self.span_err(last_span,
+                                      "at least one type parameter bound \
+                                       must be specified after the `+`");
+                    }
                     Some(bounds)
                 } else {
                     None

src/test/compile-fail/kindck-send.rs

@@ -40,7 +40,7 @@ fn test<'a,T,U:Send>(_: &'a int) {
     assert_send::<&'static Dummy>(); //~ ERROR does not fulfill `Send`
     assert_send::<&'a Dummy>(); //~ ERROR does not fulfill `Send`
     assert_send::<&'a Dummy+Send>(); //~ ERROR does not fulfill `Send`
-    assert_send::<Box<Dummy+>>(); //~ ERROR does not fulfill `Send`
+    assert_send::<Box<Dummy>>(); //~ ERROR does not fulfill `Send`
 
     // ...unless they are properly bounded
     assert_send::<&'static Dummy+Send>();

src/test/compile-fail/trailing-plus-in-bounds.rs

@@ -0,0 +1,18 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::fmt::Show;
+
+fn main() {
+    let x: Box<Show+> = box 3 as Box<Show+>;
+    //~^ ERROR at least one type parameter bound must be specified
+    //~^^ ERROR at least one type parameter bound must be specified
+}
+

src/test/compile-fail/trait-bounds-cant-coerce.rs

@@ -19,7 +19,7 @@ fn c(x: Box<Foo+Share+Send>) {
     a(x);
 }
 
-fn d(x: Box<Foo+>) {
+fn d(x: Box<Foo>) {
     a(x); //~ ERROR found no bounds
 }
 

src/test/run-pass/close-over-big-then-small-data.rs

@@ -33,11 +33,11 @@ impl<A:Clone> Invokable<A> for Invoker<A> {
     }
 }
 
-fn f<A:Clone + 'static>(a: A, b: u16) -> Box<Invokable<A>+> {
+fn f<A:Clone + 'static>(a: A, b: u16) -> Box<Invokable<A>> {
     box Invoker {
         a: a,
         b: b,
-    } as (Box<Invokable<A>>+)
+    } as (Box<Invokable<A>>)
 }
 
 pub fn main() {

src/test/run-pass/closure-syntax.rs

@@ -59,7 +59,6 @@ fn bar<'b>() {
     foo::< <'a>|int, f32, &'a int|:'b + Share -> &'a int>();
     foo::<proc()>();
     foo::<proc() -> ()>();
-    foo::<proc():>();
     foo::<proc():'static>();
     foo::<proc():Share>();
     foo::<proc<'a>(int, f32, &'a int):'static + Share -> &'a int>();

src/test/run-pass/issue-7673-cast-generically-implemented-trait.rs

@@ -20,6 +20,5 @@ pub fn main() {}
 trait A {}
 impl<T: 'static> A for T {}
 
-fn owned1<T: 'static>(a: T) { box a as Box<A+>; } /* note `:` */
 fn owned2<T: 'static>(a: Box<T>) { a as Box<A>; }
 fn owned3<T: 'static>(a: Box<T>) { box a as Box<A>; }

src/test/run-pass/proc-bounds.rs

@@ -28,7 +28,7 @@ pub fn main() {
 
 
     let a = 3;
-    bar::<proc():>(proc() {
+    bar::<proc()>(proc() {
         let b = &a;
         println!("{}", *b);
     });

src/test/run-pass/trait-bounds-basic.rs

@@ -12,22 +12,19 @@
 trait Foo {
 }
 
-fn a(_x: Box<Foo+>) {
-}
-
 fn b(_x: Box<Foo+Send>) {
 }
 
 fn c(x: Box<Foo+Share+Send>) {
-    a(x);
+    e(x);
 }
 
 fn d(x: Box<Foo+Send>) {
-    b(x);
+    e(x);
 }
 
-fn e(x: Box<Foo>) { // sugar for Box<Foo+Owned>
-    a(x);
+fn e(x: Box<Foo>) {
+    e(x);
 }
 
 pub fn main() { }