From 4a3277068b15d241c8f88d4897d2af4e7f3290b2 Mon Sep 17 00:00:00 2001
From: Campbell He <kp.campbell.he@duskmoon314.com>
Date: Tue, 21 Feb 2023 11:15:13 +0800
Subject: [PATCH] Use IndexSet in preserve_order

---
 schemars/src/flatten.rs | 5 ++++-
 schemars/src/lib.rs     | 6 +++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/schemars/src/flatten.rs b/schemars/src/flatten.rs
index 35a734fa..fee9a6aa 100644
--- a/schemars/src/flatten.rs
+++ b/schemars/src/flatten.rs
@@ -139,7 +139,10 @@ where
     }
 }
 
-impl<T: Ord> Merge for Set<T> {
+impl<T> Merge for Set<T>
+where
+    T: std::hash::Hash + Ord,
+{
     fn merge(mut self, other: Self) -> Self {
         self.extend(other);
         self
diff --git a/schemars/src/lib.rs b/schemars/src/lib.rs
index 2094c428..915f5318 100644
--- a/schemars/src/lib.rs
+++ b/schemars/src/lib.rs
@@ -295,9 +295,13 @@ pub type Map<K, V> = std::collections::BTreeMap<K, V>;
 pub type Map<K, V> = indexmap::IndexMap<K, V>;
 /// The set type used by schemars types.
 ///
-/// Currently a `BTreeSet`, but this may change to a different implementation
+/// Currently a `BTreeSet` or `IndexSet`, but this may change to a different implementation
 /// with a similar interface in a future version of schemars.
+/// The `IndexSet` will be used when the `preserve_order` feature flag is set.
+#[cfg(not(feature = "preserve_order"))]
 pub type Set<T> = std::collections::BTreeSet<T>;
+#[cfg(feature = "preserve_order")]
+pub type Set<T> = indexmap::IndexSet<T>;
 
 /// A view into a single entry in a map, which may either be vacant or occupied.
 //