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AK: Allow Optional<T&> to exist

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This implements Optional<T&> as a T*, whose presence has been missing
since the early days of Optional.
As a lot of find_foo() APIs return an Optional<T> which imposes a
pointless copy on the underlying value, and can sometimes be very
misleading, with this change, those APIs can return Optional<T&>.
This commit is contained in:
Ali Mohammad Pur 2022-04-03 15:36:34 +04:30 • committed by Andreas Kling
parent 8f1ba8db4f
commit 221ecf17d3
3 changed files with 238 additions and 1 deletions
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58
Tests/AK/TestOptional.cpp
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@ -211,3 +211,61 @@ TEST_CASE(test_copy_ctor_and_dtor_called)
static_assert(!IsDestructible<Optional<NonDestructible>>);
#endif
}
TEST_CASE(basic_optional_reference)
{
Optional<int&> x;
EXPECT_EQ(x.has_value(), false);
int a = 3;
x = a;
EXPECT_EQ(x.has_value(), true);
EXPECT_EQ(x.value(), 3);
EXPECT_EQ(&x.value(), &a);
Optional<int const&> y;
EXPECT_EQ(y.has_value(), false);
int b = 3;
y = b;
EXPECT_EQ(y.has_value(), true);
EXPECT_EQ(y.value(), 3);
EXPECT_EQ(&y.value(), &b);
static_assert(IsConst<RemoveReference<decltype(y.value())>>);
}
TEST_CASE(move_optional_reference)
{
Optional<int&> x;
EXPECT_EQ(x.has_value(), false);
int b = 3;
x = b;
EXPECT_EQ(x.has_value(), true);
EXPECT_EQ(x.value(), 3);
Optional<int&> y;
y = move(x);
EXPECT_EQ(y.has_value(), true);
EXPECT_EQ(y.value(), 3);
EXPECT_EQ(x.has_value(), false);
}
TEST_CASE(short_notation_reference)
{
StringView test = "foo";
Optional<StringView&> value = test;
EXPECT_EQ(value->length(), 3u);
EXPECT_EQ(*value, "foo");
}
TEST_CASE(comparison_reference)
{
StringView test = "foo";
Optional<StringView&> opt0;
Optional<StringView const&> opt1 = test;
Optional<String> opt2 = "foo";
Optional<StringView> opt3 = "bar";
EXPECT_NE(opt0, opt1);
EXPECT_EQ(opt1, opt2);
EXPECT_NE(opt1, opt3);
}