Conditionally provide impl From<i128> and From<u128> for Number

Author: dtolnay

src/number.rs

@@ -740,6 +740,21 @@ macro_rules! impl_from_signed {
 impl_from_unsigned!(u8, u16, u32, u64, usize);
 impl_from_signed!(i8, i16, i32, i64, isize);
 
+#[cfg(feature = "arbitrary_precision")]
+serde_if_integer128! {
+    impl From<i128> for Number {
+        fn from(i: i128) -> Self {
+            Number { n: i.to_string() }
+        }
+    }
+
+    impl From<u128> for Number {
+        fn from(u: u128) -> Self {
+            Number { n: u.to_string() }
+        }
+    }
+}
+
 impl Number {
     #[cfg(not(feature = "arbitrary_precision"))]
     // Not public API. Should be pub(crate).

src/value/from.rs

@@ -29,6 +29,13 @@ from_integer! {
     u8 u16 u32 u64 usize
 }
 
+#[cfg(feature = "arbitrary_precision")]
+serde_if_integer128! {
+    from_integer! {
+        i128 u128
+    }
+}
+
 impl From<f32> for Value {
     /// Convert 32-bit floating point number to `Value`
     ///

src/value/ser.rs

@@ -77,10 +77,10 @@ impl serde::Serializer for Serializer {
         Ok(Value::Number(value.into()))
     }
 
+    #[cfg(feature = "arbitrary_precision")]
     serde_if_integer128! {
-        #[cfg(feature = "arbitrary_precision")]
         fn serialize_i128(self, value: i128) -> Result<Value, Error> {
-            Ok(Value::Number(Number::from_string_unchecked(value.to_string())))
+            Ok(Value::Number(value.into()))
         }
     }
 
@@ -104,10 +104,10 @@ impl serde::Serializer for Serializer {
         Ok(Value::Number(value.into()))
     }
 
+    #[cfg(feature = "arbitrary_precision")]
     serde_if_integer128! {
-        #[cfg(feature = "arbitrary_precision")]
         fn serialize_u128(self, value: u128) -> Result<Value, Error> {
-            Ok(Value::Number(Number::from_string_unchecked(value.to_string())))
+            Ok(Value::Number(value.into()))
         }
     }