auto merge of #19899 : japaric/rust/unops-by-value, r=nikomatsakis

- The following operator traits now take their argument by value: `Neg`, `Not`. This breaks all existing implementations of these traits.

- The unary operation `OP a` now "desugars" to `OpTrait::op_method(a)` and consumes its argument.

[breaking-change]

---

r? @nikomatsakis This PR is very similar to the binops-by-value PR
cc @aturon

src/test/compile-fail/unop-move-semantics.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 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.
+
+// Test that move restrictions are enforced on overloaded unary operations
+
+fn move_then_borrow<T: Not<T> + Clone>(x: T) {
+    !x;
+
+    x.clone();  //~ ERROR: use of moved value
+}
+
+fn move_borrowed<T: Not<T>>(x: T, mut y: T) {
+    let m = &x;
+    let n = &mut y;
+
+    !x;  //~ ERROR: cannot move out of `x` because it is borrowed
+
+    !y;  //~ ERROR: cannot move out of `y` because it is borrowed
+}
+
+fn illegal_dereference<T: Not<T>>(mut x: T, y: T) {
+    let m = &mut x;
+    let n = &y;
+
+    !*m;  //~ ERROR: cannot move out of dereference of `&mut`-pointer
+
+    !*n;  //~ ERROR: cannot move out of dereference of `&`-pointer
+}
+
+fn main() {}

src/test/run-pass/operator-overloading.rs

@@ -31,13 +31,13 @@ impl ops::Sub<Point,Point> for Point {
 }
 
 impl ops::Neg<Point> for Point {
-    fn neg(&self) -> Point {
+    fn neg(self) -> Point {
         Point {x: -self.x, y: -self.y}
     }
 }
 
 impl ops::Not<Point> for Point {
-    fn not(&self) -> Point {
+    fn not(self) -> Point {
         Point {x: !self.x, y: !self.y }
     }
 }