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 

1 files changed, 11 insertions, 0 deletions

diff --git a/src/libstd/bitflags.rs b/src/libstd/bitflags.rs
index 2be6f5057a1..f467b77dbf4 100644
--- a/src/libstd/bitflags.rs
+++ b/src/libstd/bitflags.rs
@@ -281,6 +281,8 @@ macro_rules! bitflags {
             }
         }
 
+        // NOTE(stage0): Remove impl after a snapshot
+        #[cfg(stage0)]
         impl Not<$BitFlags> for $BitFlags {
             /// Returns the complement of this set of flags.
             #[inline]
@@ -288,6 +290,15 @@ macro_rules! bitflags {
                 $BitFlags { bits: !self.bits } & $BitFlags::all()
             }
         }
+
+        #[cfg(not(stage0))]  // NOTE(stage0): Remove cfg after a snapshot
+        impl Not<$BitFlags> for $BitFlags {
+            /// Returns the complement of this set of flags.
+            #[inline]
+            fn not(self) -> $BitFlags {
+                $BitFlags { bits: !self.bits } & $BitFlags::all()
+            }
+        }
     };
     ($(#[$attr:meta])* flags $BitFlags:ident: $T:ty {
         $($(#[$Flag_attr:meta])* const $Flag:ident = $value:expr),+,