Slightly improve performance of builders

Builders would keep a `serde_json::Map<String, Value>`, which would
require re-creating owned strings for the same parameter multiple times
in some cases, depending on builder defaults and keying strategies.

This commit uses a `std::collections::HashMap<&'static str, Value>`
internally, and moves over values to a `serde_json::Map<String, Value>`
when it comes time to sending them to the appropriate `http` module
function.

This saves the number of heap-allocated string creations on most
builders, with specific performance increase on `builder::CreateMessage`
and `builder::CreateEmbed` & co.

1 files changed, 4 insertions, 7 deletions

diff --git a/src/model/webhook.rs b/src/model/webhook.rs
index c8ae1b0..e00d018 100644
--- a/src/model/webhook.rs
+++ b/src/model/webhook.rs
@@ -7,7 +7,7 @@ use builder::ExecuteWebhook;
 #[cfg(feature = "model")]
 use internal::prelude::*;
 #[cfg(feature = "model")]
-use http;
+use {http, utils};
 
 /// A representation of a webhook, which is a low-effort way to post messages to
 /// channels. They do not necessarily require a bot user or authentication to
@@ -183,12 +183,9 @@ impl Webhook {
                                                                 wait: bool,
                                                                 f: F)
                                                                 -> Result<Option<Message>> {
-        http::execute_webhook(
-            self.id.0,
-            &self.token,
-            wait,
-            &f(ExecuteWebhook::default()).0,
-        )
+        let map = utils::hashmap_to_json_map(f(ExecuteWebhook::default()).0);
+
+        http::execute_webhook(self.id.0, &self.token, wait, &map)
     }
 
     /// Retrieves the latest information about the webhook, editing the