Auto merge of rust-lang#54240 - csmoe:nonzero_from, r=alexcrichton

Impl From<NonZero<T>> for T

Closes rust-lang#54171

r? @SimonSapin

Author: bors

src/libcore/num/mod.rs

@@ -93,6 +93,13 @@ assert_eq!(size_of::<Option<std::num::", stringify!($Ty), ">>(), size_of::<", st
 
             }
 
+            #[stable(feature = "from_nonzero", since = "1.31.0")]
+            impl From<$Ty> for $Int {
+                fn from(nonzero: $Ty) -> Self {
+                    nonzero.0 .0
+                }
+            }
+
             impl_nonzero_fmt! {
                 (Debug, Display, Binary, Octal, LowerHex, UpperHex) for $Ty
             }

src/libcore/tests/nonzero.rs

@@ -121,3 +121,10 @@ fn test_match_nonzero_const_pattern() {
         _ => panic!("Expected the const item as a pattern to match.")
     }
 }
+
+#[test]
+fn test_from_nonzero() {
+    let nz = NonZeroU32::new(1).unwrap();
+    let num: u32 = nz.into();
+    assert_eq!(num, 1u32);
+}