Auto merge of #24500 - pnkfelix:oflo-checked-neg, r=nikomatsakis

Add conditional overflow-checking to signed negate operator.

I argue this can land independently of #24420 , because one can write the implementation of `wrapped_neg()` inline if necessary (as illustrated in two cases on this PR).

This needs to go into beta channel.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index c7714afc4fa..a056e585fee 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -1321,7 +1321,11 @@ macro_rules! int_impl {
         #[stable(feature = "rust1", since = "1.0.0")]
         #[inline]
         pub fn abs(self) -> $T {
-            if self.is_negative() { -self } else { self }
+            if self.is_negative() {
+                self.wrapping_neg()
+            } else {
+                self
+            }
         }
 
         /// Returns a number representing sign of `self`.