make implicit conversions non-reentrant (fixes #1035) (#1037)

diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 842991a..2221906 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -291,6 +291,17 @@
         .def(py::init<int, const std::string &>())
         .def_readwrite("field1", &BraceInitialization::field1)
         .def_readwrite("field2", &BraceInitialization::field2);
+
+    // test_reentrant_implicit_conversion_failure
+    // #1035: issue with runaway reentrant implicit conversion
+    struct BogusImplicitConversion {
+        BogusImplicitConversion(const BogusImplicitConversion &) { }
+    };
+
+    py::class_<BogusImplicitConversion>(m, "BogusImplicitConversion")
+        .def(py::init<const BogusImplicitConversion &>());
+
+    py::implicitly_convertible<int, BogusImplicitConversion>();
 }
 
 template <int N> class BreaksBase { public: virtual ~BreaksBase() = default; };