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 

2 files changed, 25 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),+,
diff --git a/src/libstd/time/duration.rs b/src/libstd/time/duration.rs
index 8c4a5a6b8c7..85ed27853c4 100644
--- a/src/libstd/time/duration.rs
+++ b/src/libstd/time/duration.rs
@@ -265,6 +265,8 @@ impl Duration {
     }
 }
 
+// NOTE(stage0): Remove impl after a snapshot
+#[cfg(stage0)]
 impl Neg<Duration> for Duration {
     #[inline]
     fn neg(&self) -> Duration {
@@ -276,6 +278,18 @@ impl Neg<Duration> for Duration {
     }
 }
 
+#[cfg(not(stage0))]  // NOTE(stage0): Remove cfg after a snapshot
+impl Neg<Duration> for Duration {
+    #[inline]
+    fn neg(self) -> Duration {
+        if self.nanos == 0 {
+            Duration { secs: -self.secs, nanos: 0 }
+        } else {
+            Duration { secs: -self.secs - 1, nanos: NANOS_PER_SEC - self.nanos }
+        }
+    }
+}
+
 // NOTE(stage0): Remove impl after a snapshot
 #[cfg(stage0)]
 impl Add<Duration,Duration> for Duration {