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Commit d48d801b authored by Dominik Laskowski's avatar Dominik Laskowski
Browse files

FTL: Downcast to Optional<T> implicitly 

The expression `ftl::Optional(std::optional(T()))` should not have type
`ftl::Optional<std::optional<T>>`.

Bug: 185536303
Test: ftl_test
Change-Id: I931cc58b985e7c41037ed50bc68abdc8028c4bdd
parent a957c1c1

include/ftl/optional.h

+7 −1
Original line number Diff line number Diff line
@@ -32,6 +32,9 @@ template <typename T> 
struct Optional final : std::optional<T> {

  using std::optional<T>::optional;



  // Implicit downcast.

  Optional(std::optional<T> other) : std::optional<T>(std::move(other)) {}



  using std::optional<T>::has_value;

  using std::optional<T>::value;
@@ -94,8 +97,11 @@ struct Optional final : std::optional<T> { 
  }

};



// Deduction guide.

// Deduction guides.

template <typename T>

Optional(T) -> Optional<T>;



template <typename T>

Optional(std::optional<T>) -> Optional<T>;



}  // namespace android::ftl

libs/ftl/optional_test.cpp

+23 −0
Original line number Diff line number Diff line
@@ -33,6 +33,29 @@ namespace android::test { 
using ftl::Optional;

using ftl::StaticVector;



TEST(Optional, Construct) {

  // Empty.

  EXPECT_EQ(std::nullopt, Optional<int>());

  EXPECT_EQ(std::nullopt, Optional<std::string>(std::nullopt));



  // Value.

  EXPECT_EQ('?', Optional('?'));

  EXPECT_EQ(""s, Optional(std::string()));



  // In place.

  EXPECT_EQ("???"s, Optional<std::string>(std::in_place, 3u, '?'));

  EXPECT_EQ("abc"s, Optional<std::string>(std::in_place, {'a', 'b', 'c'}));



  // Implicit downcast.

  {

    Optional opt = std::optional("test"s);

    static_assert(std::is_same_v<decltype(opt), Optional<std::string>>);



    ASSERT_TRUE(opt);

    EXPECT_EQ(opt.value(), "test"s);

  }

}



TEST(Optional, Transform) {

  // Empty.

  EXPECT_EQ(std::nullopt, Optional<int>().transform([](int) { return 0; }));