Auto merge of #51404 - clarcharr:never_hash, r=KodrAus

bors · bors · commit 4f2936393e27 · 2018-06-17T22:25:34.000Z
impl Hash for !

This was missing in some generic code I was writing and I figured that it would be worthwhile to add this. Blanket-requiring these traits to allow usage of errors in `HashSet`s and `HashMap`s isn't too unreasonable of a use case, and a prerequisite for allowing `!` as an error in such situations is this impl.
diff --git a/src/libcore/hash/mod.rs b/src/libcore/hash/mod.rs
@@ -603,6 +603,13 @@ mod impls {
         }
     }
 
+    #[stable(feature = "never_hash", since = "1.29.0")]
+    impl Hash for ! {
+        fn hash<H: Hasher>(&self, _: &mut H) {
+            *self
+        }
+    }
+
     macro_rules! impl_hash_tuple {
         () => (
             #[stable(feature = "rust1", since = "1.0.0")]

Original file line number	Diff line number	Diff line change
`@@ -603,6 +603,13 @@ mod impls {`
`603`	`603`	`}`
`604`	`604`	`}`
`605`	`605`
	`606`	`+ #[stable(feature = "never_hash", since = "1.29.0")]`
	`607`	`+ impl Hash for ! {`
	`608`	`+ fn hash<H: Hasher>(&self, _: &mut H) {`
	`609`	`+ *self`
	`610`	`+ }`
	`611`	`+ }`
	`612`	`+`
`606`	`613`	`macro_rules! impl_hash_tuple {`
`607`	`614`	`() => (`
`608`	`615`	`#[stable(feature = "rust1", since = "1.0.0")]`