Add a test for NumPy scalar conversion

tests/test_numpy_dtypes.cpp

@@ -298,6 +298,9 @@ test_initializer numpy_dtypes([](py::module &m) {
         return;
     }
 
+    // typeinfo may be registered before the dtype descriptor for scalar casts to work...
+    py::class_<SimpleStruct>(m, "SimpleStruct");
+
     PYBIND11_NUMPY_DTYPE(SimpleStruct, x, y, z);
     PYBIND11_NUMPY_DTYPE(PackedStruct, x, y, z);
     PYBIND11_NUMPY_DTYPE(NestedStruct, a, b);
@@ -306,6 +309,11 @@ test_initializer numpy_dtypes([](py::module &m) {
     PYBIND11_NUMPY_DTYPE(StringStruct, a, b);
     PYBIND11_NUMPY_DTYPE(EnumStruct, e1, e2);
 
+    // ... or after...
+    py::class_<PackedStruct>(m, "PackedStruct");
+
+    // ... or not at all
+
     m.def("create_rec_simple", &create_recarray<SimpleStruct>);
     m.def("create_rec_packed", &create_recarray<PackedStruct>);
     m.def("create_rec_nested", &create_nested);
@@ -324,6 +332,9 @@ test_initializer numpy_dtypes([](py::module &m) {
     m.def("test_array_ctors", &test_array_ctors);
     m.def("test_dtype_ctors", &test_dtype_ctors);
     m.def("test_dtype_methods", &test_dtype_methods);
+    m.def("f_simple", [](SimpleStruct s) { return s.y * 10; });
+    m.def("f_packed", [](PackedStruct s) { return s.y * 10; });
+    m.def("f_nested", [](NestedStruct s) { return s.a.y * 10; });
 });
 
 #undef PYBIND11_PACKED

tests/test_numpy_dtypes.py

@@ -174,3 +174,25 @@ def test_signature(doc):
     from pybind11_tests import create_rec_nested
 
     assert doc(create_rec_nested) == "create_rec_nested(arg0: int) -> numpy.ndarray[NestedStruct]"
+
+
+@pytest.requires_numpy
+def test_scalar_conversion():
+    from pybind11_tests import (create_rec_simple, f_simple,
+                                create_rec_packed, f_packed,
+                                create_rec_nested, f_nested,
+                                create_enum_array)
+
+    n = 3
+    arrays = [create_rec_simple(n), create_rec_packed(n),
+              create_rec_nested(n), create_enum_array(n)]
+    funcs = [f_simple, f_packed, f_nested]
+
+    for i, func in enumerate(funcs):
+        for j, arr in enumerate(arrays):
+            if i == j:
+                assert [func(arr[k]) for k in range(n)] == [k * 10 for k in range(n)]
+            else:
+                with pytest.raises(TypeError) as excinfo:
+                    func(arr[0])
+                assert 'incompatible function arguments' in str(excinfo.value)