From e040a8c7175dae3a369cc2aa244172b7617e047c Mon Sep 17 00:00:00 2001
From: Martin Hochel <martinhochel@microsoft.com>
Date: Fri, 28 Jun 2024 12:15:59 +0200
Subject: [PATCH 1/2] fix(merge-styles): keep same type output for
 DeepPartialV2 to match original DeepPartial

---
 packages/merge-styles/src/DeepPartial.ts | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/packages/merge-styles/src/DeepPartial.ts b/packages/merge-styles/src/DeepPartial.ts
index ca351bd5feb54..cfca387a79bee 100644
--- a/packages/merge-styles/src/DeepPartial.ts
+++ b/packages/merge-styles/src/DeepPartial.ts
@@ -1,3 +1,5 @@
+/* eslint-disable @fluentui/max-len */
+
 /**
  * TypeScript type to return a deep partial object (each property can be undefined, recursively.)
  * @deprecated - This type will hit infinite type instantiation recursion. Please use {@link DeepPartialV2}
@@ -13,8 +15,14 @@ type DeepPartialObject<T> = {
   [Key in keyof T]?: DeepPartialV2<T[Key]>;
 };
 
+/**
+ * Why `T extends Function ? {}` :
+ * While this transform is incorrect, in order not run into infinite type instantiation to maintain type creation compatibility with original {@link DeepPartial} we need to hit `[P in keyof T]? T[P]` part of the mapped type from original,
+ * which would transform to bottom type `{}` if `Function` would be `T`
+ *
+ */
 export type DeepPartialV2<T> = T extends Function
-  ? T
+  ? {}
   : T extends Array<infer U>
   ? IDeepPartialArray<U>
   : T extends object

From 7b492b716be54b68d52e728182388170db72a883 Mon Sep 17 00:00:00 2001
From: Martin Hochel <martinhochel@microsoft.com>
Date: Fri, 28 Jun 2024 12:16:42 +0200
Subject: [PATCH 2/2] change file

---
 ...-merge-styles-917f7ae8-0a61-47db-83f7-e29e8264ac4e.json | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 change/@fluentui-merge-styles-917f7ae8-0a61-47db-83f7-e29e8264ac4e.json

diff --git a/change/@fluentui-merge-styles-917f7ae8-0a61-47db-83f7-e29e8264ac4e.json b/change/@fluentui-merge-styles-917f7ae8-0a61-47db-83f7-e29e8264ac4e.json
new file mode 100644
index 0000000000000..a8cdf823eb0b4
--- /dev/null
+++ b/change/@fluentui-merge-styles-917f7ae8-0a61-47db-83f7-e29e8264ac4e.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: keep same type output for DeepPartialV2 to match original DeepPartial",
+  "packageName": "@fluentui/merge-styles",
+  "email": "martinhochel@microsoft.com",
+  "dependentChangeType": "patch"
+}