Add 'contrib/catch2/' from commit 'bc524d70253a4ab2fe40c3ca3e5666e267c0a4d1'

git-subtree-dir: contrib/catch2
git-subtree-mainline: a8b0ea58e60bb0326b7f7c8f3c736d89ce9ef1df
git-subtree-split: bc524d70253a4ab2fe40c3ca3e5666e267c0a4d1

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diff --git a/contrib/catch2/examples/310-Gen-VariablesInGenerators.cpp b/contrib/catch2/examples/310-Gen-VariablesInGenerators.cpp
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+++ b/contrib/catch2/examples/310-Gen-VariablesInGenerators.cpp
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+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+
+// 310-Gen-VariablesInGenerator.cpp
+// Shows how to use variables when creating generators.
+
+// Note that using variables inside generators is dangerous and should
+// be done only if you know what you are doing, because the generators
+// _WILL_ outlive the variables -- thus they should be either captured
+// by value directly, or copied by the generators during construction.
+
+#include <catch2/catch_test_macros.hpp>
+#include <catch2/generators/catch_generators_adapters.hpp>
+#include <catch2/generators/catch_generators_random.hpp>
+
+TEST_CASE("Generate random doubles across different ranges",
+          "[generator][example][advanced]") {
+    // Workaround for old libstdc++
+    using record = std::tuple<double, double>;
+    // Set up 3 ranges to generate numbers from
+    auto r = GENERATE(table<double, double>({
+        record{3, 4},
+        record{-4, -3},
+        record{10, 1000}
+    }));
+
+    // This will not compile (intentionally), because it accesses a variable
+    // auto number = GENERATE(take(50, random(std::get<0>(r), std::get<1>(r))));
+
+   // GENERATE_COPY copies all variables mentioned inside the expression
+   // thus this will work.
+    auto number = GENERATE_COPY(take(50, random(std::get<0>(r), std::get<1>(r))));
+
+    REQUIRE(std::abs(number) > 0);
+}
+
+// Compiling and running this file will result in 150 successful assertions
+