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

Change-Id: I9636a41ad44b4218293833fd3e9456d9b07c731b

third_party/immer/test/box/vector-of-boxes-transient.cpp

@@ -0,0 +1,36 @@
+//
+// 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
+//
+
+#include <immer/box.hpp>
+#include <immer/vector.hpp>
+#include <immer/vector_transient.hpp>
+
+#include <catch.hpp>
+
+TEST_CASE("issue-33")
+{
+    using Element = immer::box<std::string>;
+    auto vect     = immer::vector<Element>{};
+
+    // this one works fine
+    for (auto i = 0; i < 100; ++i) {
+        vect = vect.push_back(Element("x"));
+    }
+
+    // this one doesn't compile
+    auto t = vect.transient();
+
+    for (auto i = 0; i < 100; ++i) {
+        t.push_back(Element("x"));
+    }
+
+    vect = t.persistent();
+
+    CHECK(*vect[0] == "x");
+    CHECK(*vect[99] == "x");
+}