merge(3p/immer): Subtree merge at 'ad3e3556d' as 'third_party/immer'

Change-Id: I9636a41ad44b4218293833fd3e9456d9b07c731b

third_party/immer/test/flex_vector/issue-45.cpp

@@ -0,0 +1,35 @@
+//
+// immer: immutable data structures for C++
+// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
+//
+// This software is distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
+//
+
+// Thanks Guiguiprim for reporting this issue
+// https://github.com/arximboldi/immer/issues/46
+
+#include <immer/flex_vector.hpp>
+#include <immer/vector.hpp>
+#include <immer/vector_transient.hpp>
+
+#include <catch.hpp>
+
+#if IMMER_CXX_STANDARD >= 17
+
+#include <variant>
+
+TEST_CASE("error when erasing an element from a "
+          "immer::flex_vector<std::variant/optional/any>")
+{
+    using Vector = immer::flex_vector<std::variant<int, double>>;
+    // using Vector = immer::flex_vector<std::optional<int>>;
+    // using Vector = immer::flex_vector<std::any>;
+
+    Vector v{1, 2, 3, 4};
+    Vector v2 = v.erase(2);
+
+    CHECK(v2.size() == 3);
+}
+
+#endif