Use compatible RNG with shuffle (#1688)

Fixes #1687

NEWS.md

@@ -1,5 +1,10 @@
 # testthat (development version)
 
+* Fixed an issue that could prevent compilation of Catch unit tests with
+  LLVM 15. In the interim, packages needing a local workaround can set
+  `PKG_CPPFLAGS = -DCATCH_CONFIG_CPP11_NO_SHUFFLE` in their `src/Makevars`.
+  (@kevinushey, #1687)
+
 * `local_reproducible_output` will no longer attempt to set the local language
   when an R version is used that was not compiled with natural language support
   (NLS), which would previously emit non-test-related warnings during testing

inst/include/testthat/vendor/catch.h

@@ -7165,27 +7165,23 @@ namespace Catch {
 // #included from: catch_test_case_registry_impl.hpp
 #define TWOBLUECUBES_CATCH_TEST_CASE_REGISTRY_IMPL_HPP_INCLUDED
 
-#include <vector>
+#include <algorithm>
 #include <set>
 #include <sstream>
-#include <algorithm>
+#include <vector>
+
+#ifdef CATCH_CONFIG_CPP11_SHUFFLE
+#include <random>
+#endif
 
 namespace Catch {
 
     struct RandomNumberGenerator {
-        typedef std::ptrdiff_t result_type;
-
-        result_type operator()( result_type n ) const { return rand() % n; }
-
-#ifdef CATCH_CONFIG_CPP11_SHUFFLE
-        static constexpr result_type min() { return 0; }
-        static constexpr result_type max() { return 1000000; }
-        result_type operator()() const { return rand() % max(); }
-#endif
         template<typename V>
         static void shuffle( V& vector ) {
-            RandomNumberGenerator rng;
 #ifdef CATCH_CONFIG_CPP11_SHUFFLE
+            std::random_device device;
+            std::mt19937 rng( device() );
             std::shuffle( vector.begin(), vector.end(), rng );
 #else
             random_shuffle( vector.begin(), vector.end(), rng );