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, 5 insertions, 1 deletions

diff --git a/src/model/channel/embed.rs b/src/model/channel/embed.rs
index 435f706..74c503d 100644
--- a/src/model/channel/embed.rs
+++ b/src/model/channel/embed.rs
@@ -4,6 +4,8 @@ use utils::Colour;
 use internal::prelude::*;
 #[cfg(feature = "model")]
 use builder::CreateEmbed;
+#[cfg(feature = "model")]
+use utils;
 
 /// Represents a rich embed which allows using richer markdown, multiple fields
 /// and more. This was heavily inspired by [slack's attachments].
@@ -89,7 +91,9 @@ impl Embed {
     #[inline]
     pub fn fake<F>(f: F) -> Value
         where F: FnOnce(CreateEmbed) -> CreateEmbed {
-        Value::Object(f(CreateEmbed::default()).0)
+        let map = utils::hashmap_to_json_map(f(CreateEmbed::default()).0);
+
+        Value::Object(map)
     }
 }