Fix negative nonces failing to deserialize

Negative message nonces caused deserialization errors, as serde would
not deserialize integers into strings.

To fix this, change `Message::nonce` into an `Option<Snowflake>` from an
`Option<String>`. This new `Snowflake` is a wrapper around an `i64`. Use
a new `I64Visitor` to deserialize i64s, u64s, and strs into the wanted
i64.

2 files changed, 27 insertions, 0 deletions

diff --git a/tests/resources/message_create_2.json b/tests/resources/message_create_2.json
new file mode 100644
index 0000000..f999397
--- /dev/null
+++ b/tests/resources/message_create_2.json
@@ -0,0 +1,23 @@
+{
+  "type": 0,
+  "tts": false,
+  "timestamp": "2017-01-01T01:01:01.100000+00:00",
+  "pinned": false,
+  "nonce": -6000000000000000,
+  "mentions": [],
+  "mention_roles": [],
+  "mention_everyone": false,
+  "id": "300000000000000000",
+  "embeds": [],
+  "edited_timestamp": null,
+  "content": "fake",
+  "channel_id": "100000000000000000",
+  "author": {
+    "username": "fake",
+    "id": "300000000000000000",
+    "discriminator": "1234",
+    "bot": true,
+    "avatar": "f133549aac3208319a9fbc3c12345678"
+  },
+  "attachments": []
+}
diff --git a/tests/test_deser.rs b/tests/test_deser.rs
index f4387bc..1024492 100644
--- a/tests/test_deser.rs
+++ b/tests/test_deser.rs
@@ -111,7 +111,11 @@ fn guild_update() {
 
 #[test]
 fn message_create() {
+    // standard
     p!(MessageCreateEvent, "message_create_1");
+
+    // negative nonce
+    p!(MessageCreateEvent, "message_create_2");
 }
 
 #[test]