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'optional<T&>::and_then(F&& f) &&' calls f with lvalue reference

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This makes sense. The 'optional' is an rvalue, but its contained type
remains an lvalue reference. I.e.

int i = 3;
optional<int&>{i}.and_then([](int& r){return optional<int&>{++r});

The optional r-value still refers to 'i', which is not an r-value.
This commit is contained in:
Bj?rn Fahller
2018-06-03 12:09:17 +02:00
parent f82f78b5b6
commit 5143f9577a
2 changed files with 11 additions and 6 deletions
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tests/extensions.cpp
+7 -2
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@@ -237,9 +237,14 @@ TEST_CASE("Monadic operations", "[monadic]") {
REQUIRE(!o18r);
const tl::optional<int> o19 = tl::nullopt;
auto o19r =
std::move(o19).and_then([](int i) { return tl::make_optional(42); });
auto o19r = std::move(o19).and_then([](int i) { return tl::make_optional(42); });
REQUIRE(!o19r);
int i = 3;
tl::optional<int&> o20{i};
std::move(o20).and_then([](int& r){return tl::optional<int&>{++r};});
REQUIRE(o20);
REQUIRE(i == 4);
}
SECTION("constexpr and_then") {