AK: Introduce ability to default-initialize a Variant

I noticed that Variant<Empty, …> is a somewhat common pattern while working on SerenityOS#10080, and this will simplify a few use-cases. :^)
fleximus · Sep 20, 2021 · 743470c · 743470c
1 parent f261b68
commit 743470c
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Showing 2 changed files with 12 additions and 1 deletion.
diff --git a/AK/Variant.h b/AK/Variant.h
@@ -210,7 +210,11 @@ struct Variant
  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
@@ -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>());
+}