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[libcxx][test] Silence nodiscard warnings for std::expected (#119174)
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I'm exploring marking microsoft/STL's std::expected as [[nodiscard]],
which affects all functions returning std::expected, including its
own monadic member functions.

As usual, libc++'s test suite contains calls to these member functions
to make sure they compile, but it's discarding the returns. I'm adding
void casts to silence the [[nodiscard]] warnings without altering
what the test is covering.
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@StephanTLavavej
StephanTLavavej authored Dec 10, 2024
1 parent f408171 commit cb4433b
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Showing 4 changed files with 40 additions and 40 deletions.
16 changes: 8 additions & 8 deletions libcxx/test/std/utilities/expected/expected.expected/monadic/and_then.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -263,23 +263,23 @@ constexpr void test_val_types() {
constexpr void test_sfinae() {
std::expected<NonConst, int> e(std::unexpected<int>(2));
auto l = [](auto&& x) { return x.non_const(); };
e.and_then(l);
std::move(e).and_then(l);
(void)e.and_then(l);
(void)std::move(e).and_then(l);
}

constexpr void test_move_only_error_type() {
// Test &&
{
std::expected<int, MoveOnlyErrorType> e;
auto l = [](int) { return std::expected<int, MoveOnlyErrorType>{}; };
std::move(e).and_then(l);
(void)std::move(e).and_then(l);
}

// Test const&&
{
const std::expected<int, MoveOnlyErrorType> e;
auto l = [](const int) { return std::expected<int, MoveOnlyErrorType>{}; };
std::move(e).and_then(l);
(void)std::move(e).and_then(l);
}
}

Expand All @@ -296,10 +296,10 @@ constexpr bool test() {
return std::expected<int, int>();
};

e.and_then(never_called);
std::move(e).and_then(never_called);
ce.and_then(never_called);
std::move(ce).and_then(never_called);
(void)e.and_then(never_called);
(void)std::move(e).and_then(never_called);
(void)ce.and_then(never_called);
(void)std::move(ce).and_then(never_called);

return true;
}
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20 changes: 10 additions & 10 deletions libcxx/test/std/utilities/expected/expected.expected/monadic/or_else.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -178,37 +178,37 @@ struct NonConst {
constexpr void test_sfinae() {
std::expected<int, NonConst> e{1};
auto l = [](auto&& x) { return x.non_const(); };
e.or_else(l);
std::move(e).or_else(l);
(void)e.or_else(l);
(void)std::move(e).or_else(l);
}

constexpr void test_move_only_error_type() {
// Test &
{
std::expected<int, MoveOnlyErrorType> e;
auto l = [](MoveOnlyErrorType&) { return std::expected<int, int>{}; };
e.or_else(l);
(void)e.or_else(l);
}

// Test const&
{
const std::expected<int, MoveOnlyErrorType> e;
auto l = [](const MoveOnlyErrorType&) { return std::expected<int, int>{}; };
e.or_else(l);
(void)e.or_else(l);
}

// Test &&
{
std::expected<int, MoveOnlyErrorType> e;
auto l = [](MoveOnlyErrorType&&) { return std::expected<int, int>{}; };
std::move(e).or_else(l);
(void)std::move(e).or_else(l);
}

// Test const&&
{
const std::expected<int, MoveOnlyErrorType> e;
auto l = [](const MoveOnlyErrorType&&) { return std::expected<int, int>{}; };
std::move(e).or_else(l);
(void)std::move(e).or_else(l);
}
}

Expand All @@ -225,10 +225,10 @@ constexpr bool test() {
return std::expected<int, int>();
};

e.or_else(never_called);
std::move(e).or_else(never_called);
ce.or_else(never_called);
std::move(ce).or_else(never_called);
(void)e.or_else(never_called);
(void)std::move(e).or_else(never_called);
(void)ce.or_else(never_called);
(void)std::move(ce).or_else(never_called);
return true;
}

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24 changes: 12 additions & 12 deletions libcxx/test/std/utilities/expected/expected.expected/monadic/transform.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -187,27 +187,27 @@ constexpr void test_val_types() {
constexpr void test_take_val_return_void() {
std::expected<int, int> e(1);
int val = 0;
e.transform([&val]<typename T>(T&&) -> void {
(void)e.transform([&val]<typename T>(T&&) -> void {
static_assert(std::is_same_v<T, int&>);
assert(val == 0);
val = 1;
});
assert(val == 1);
std::move(e).transform([&val]<typename T>(T&&) -> void {
(void)std::move(e).transform([&val]<typename T>(T&&) -> void {
static_assert(std::is_same_v<T, int>);
assert(val == 1);
val = 2;
});

const auto& ce = e;
assert(val == 2);
ce.transform([&val]<typename T>(T&&) -> void {
(void)ce.transform([&val]<typename T>(T&&) -> void {
static_assert(std::is_same_v<T, const int&>);
assert(val == 2);
val = 3;
});
assert(val == 3);
std::move(ce).transform([&val]<typename T>(T&&) -> void {
(void)std::move(ce).transform([&val]<typename T>(T&&) -> void {
static_assert(std::is_same_v<T, const int>);
assert(val == 3);
val = 4;
Expand All @@ -227,8 +227,8 @@ constexpr void test_direct_non_list_init() {
constexpr void test_sfinae() {
std::expected<NonConst, int> e(std::unexpected<int>(2));
auto l = [](auto&& x) { return x.non_const(); };
e.transform(l);
std::move(e).transform(l);
(void)e.transform(l);
(void)std::move(e).transform(l);

std::expected<int, int> e1(std::unexpected<int>(1));
const auto& ce1 = e1;
Expand All @@ -237,25 +237,25 @@ constexpr void test_sfinae() {
return std::expected<int, int>();
};

e1.transform(never_called);
std::move(e1).transform(never_called);
ce1.and_then(never_called);
std::move(ce1).transform(never_called);
(void)e1.transform(never_called);
(void)std::move(e1).transform(never_called);
(void)ce1.transform(never_called);
(void)std::move(ce1).transform(never_called);
}

constexpr void test_move_only_error_type() {
// Test &&
{
std::expected<int, MoveOnlyErrorType> e;
auto l = [](int) { return 0; };
std::move(e).transform(l);
(void)std::move(e).transform(l);
}

// Test const&&
{
const std::expected<int, MoveOnlyErrorType> e;
auto l = [](const int) { return 0; };
std::move(e).transform(l);
(void)std::move(e).transform(l);
}
}

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20 changes: 10 additions & 10 deletions libcxx/test/std/utilities/expected/expected.expected/monadic/transform_error.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -197,8 +197,8 @@ constexpr void test_direct_non_list_init() {
constexpr void test_sfinae() {
std::expected<int, NonConst> e(2);
auto l = [](auto&& x) { return x.non_const(); };
e.transform_error(l);
std::move(e).transform_error(l);
(void)e.transform_error(l);
(void)std::move(e).transform_error(l);

std::expected<int, int> e1;
const auto& ce1 = e1;
Expand All @@ -208,39 +208,39 @@ constexpr void test_sfinae() {
return 0;
};

e1.transform_error(never_called);
std::move(e1).transform_error(never_called);
ce1.transform_error(never_called);
std::move(ce1).transform_error(never_called);
(void)e1.transform_error(never_called);
(void)std::move(e1).transform_error(never_called);
(void)ce1.transform_error(never_called);
(void)std::move(ce1).transform_error(never_called);
}

constexpr void test_move_only_error_type() {
// Test &
{
std::expected<int, MoveOnlyErrorType> e;
auto l = [](MoveOnlyErrorType&) { return 0; };
e.transform_error(l);
(void)e.transform_error(l);
}

// Test const&
{
const std::expected<int, MoveOnlyErrorType> e;
auto l = [](const MoveOnlyErrorType&) { return 0; };
e.transform_error(l);
(void)e.transform_error(l);
}

// Test &&
{
std::expected<int, MoveOnlyErrorType> e;
auto l = [](MoveOnlyErrorType&&) { return 0; };
std::move(e).transform_error(l);
(void)std::move(e).transform_error(l);
}

// Test const&&
{
const std::expected<int, MoveOnlyErrorType> e;
auto l = [](const MoveOnlyErrorType&&) { return 0; };
std::move(e).transform_error(l);
(void)std::move(e).transform_error(l);
}
}

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