Rollup merge of #131377 - rick-de-water:nonzero-exp, r=dtolnay

Add LowerExp and UpperExp implementations to NonZero

Adds `LowerExp` and `UpperExp` trait implementations to `NonZero`, as discussed in rust-lang/libs-team#458.

I had to modify the macro to mark the new impls with a different rust version. Let me know if this is the right way to do it (first timer here!)

library/core/src/num/nonzero.rs

@@ -110,26 +110,40 @@ unsafe impl ZeroablePrimitive for $primitive {
 pub struct NonZero<T: ZeroablePrimitive>(T::NonZeroInner);
 
 macro_rules! impl_nonzero_fmt {
-    ($Trait:ident) => {
-        #[stable(feature = "nonzero", since = "1.28.0")]
-        impl<T> fmt::$Trait for NonZero<T>
-        where
-            T: ZeroablePrimitive + fmt::$Trait,
-        {
-            #[inline]
-            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-                self.get().fmt(f)
+    ($(#[$Attribute:meta] $Trait:ident)*) => {
+        $(
+            #[$Attribute]
+            impl<T> fmt::$Trait for NonZero<T>
+            where
+                T: ZeroablePrimitive + fmt::$Trait,
+            {
+                #[inline]
+                fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                    self.get().fmt(f)
+                }
             }
-        }
+        )*
     };
 }
 
-impl_nonzero_fmt!(Debug);
-impl_nonzero_fmt!(Display);
-impl_nonzero_fmt!(Binary);
-impl_nonzero_fmt!(Octal);
-impl_nonzero_fmt!(LowerHex);
-impl_nonzero_fmt!(UpperHex);
+impl_nonzero_fmt! {
+    #[stable(feature = "nonzero", since = "1.28.0")]
+    Debug
+    #[stable(feature = "nonzero", since = "1.28.0")]
+    Display
+    #[stable(feature = "nonzero", since = "1.28.0")]
+    Binary
+    #[stable(feature = "nonzero", since = "1.28.0")]
+    Octal
+    #[stable(feature = "nonzero", since = "1.28.0")]
+    LowerHex
+    #[stable(feature = "nonzero", since = "1.28.0")]
+    UpperHex
+    #[stable(feature = "nonzero_fmt_exp", since = "CURRENT_RUSTC_VERSION")]
+    LowerExp
+    #[stable(feature = "nonzero_fmt_exp", since = "CURRENT_RUSTC_VERSION")]
+    UpperExp
+}
 
 macro_rules! impl_nonzero_auto_trait {
     (unsafe $Trait:ident) => {

library/core/tests/nonzero.rs

@@ -354,3 +354,14 @@ fn test_signed_nonzero_neg() {
     assert_eq!((-NonZero::<i128>::new(1).unwrap()).get(), -1);
     assert_eq!((-NonZero::<i128>::new(-1).unwrap()).get(), 1);
 }
+
+#[test]
+fn test_nonzero_fmt() {
+    let i = format!("{0}, {0:?}, {0:x}, {0:X}, {0:#x}, {0:#X}, {0:o}, {0:b}, {0:e}, {0:E}", 42);
+    let nz = format!(
+        "{0}, {0:?}, {0:x}, {0:X}, {0:#x}, {0:#X}, {0:o}, {0:b}, {0:e}, {0:E}",
+        NonZero::new(42).unwrap()
+    );
+
+    assert_eq!(i, nz);
+}