(De)serializing any type from a (de)serializable type

_src/Deserializing_any_type_from_deserializable_type.md

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+# (De)serializing any type from a (de)serializable type
+
+Sometime it's practical to (de)serialize a field of a type that does not implement (de)serialize itself from a field that does.
+
+Example:
+
+```rust
+use std::sync::atomic::AtomicU64;
+use serde::{Deserialize, Deserializer};
+
+fn deserialize_atomic_u64<'de, D>(deserializer: D) -> Result<AtomicU64, D::Error> where D: Deserializer<'de> {
+    // Note: Option<u64> implements Deserialize, so we can just tell serde to deserialize an Option<u64> and use the result
+    let value = Option::<u64>::deserialize(deserializer)?;
+    Ok(AtomicU64::new(value.unwrap_or_default()))
+}
+
+# #[allow(dead_code)]
+struct Foo {
+    // Note: the same trick works for serialize_with as well
+    #[serde(deserialize_with="deserialize_atomic_u64")]
+    atomic: AtomicU64,
+}
+#
+# fn main() {}
+```