From 743470c8f299419199c578efc80e405a8ec0e4d0 Mon Sep 17 00:00:00 2001
From: Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
Date: Sun, 19 Sep 2021 22:10:51 +0200
Subject: [PATCH] AK: Introduce ability to default-initialize a Variant
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

I noticed that Variant<Empty, …> is a somewhat common pattern while
working on #10080, and this will simplify a few use-cases. :^)
---
 AK/Variant.h             | 6 +++++-
 Tests/AK/TestVariant.cpp | 7 +++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/AK/Variant.h b/AK/Variant.h
index f757e2a3ac..dae5cd7272 100644
--- a/AK/Variant.h
+++ b/AK/Variant.h
@@ -210,7 +210,11 @@ public:
     template<typename... NewTs>
     friend struct Variant;
 
-    Variant() = delete;
+    Variant() requires(!can_contain<Empty>()) = delete;
+    Variant() requires(can_contain<Empty>())
+        : Variant(Empty())
+    {
+    }
 
 #ifdef AK_HAS_CONDITIONALLY_TRIVIAL
     Variant(const Variant&) requires(!(IsCopyConstructible<Ts> && ...)) = delete;
diff --git a/Tests/AK/TestVariant.cpp b/Tests/AK/TestVariant.cpp
index 8175b695da..f05c629022 100644
--- a/Tests/AK/TestVariant.cpp
+++ b/Tests/AK/TestVariant.cpp
@@ -219,3 +219,10 @@ TEST_CASE(copy_assign)
         EXPECT_EQ(the_value.get<String>(), "Hello, world!");
     }
 }
+
+TEST_CASE(default_empty)
+{
+    Variant<Empty, int> my_variant;
+    EXPECT(my_variant.has<Empty>());
+    EXPECT(!my_variant.has<int>());
+}