Numpy structured arrays cannot be mapped to a struct if the hierarchy is deeper than two levels

[sjdv1982]

Level 0: dtype => float, works
Level 1: structured dtype => [(name: float), (name: float), ... ], works
Level 2: structured dtype => [(name: [level 1 dtype] ), ... ], works
Level 3: structured dtype => [(name: [level 2 dtype] ), ... ], does not work

IPython notebook attached
cython-bug-notebook.zip

%load_ext Cython

%%cython -a
import numpy as np
cimport numpy as np

cdef struct Coordinate:
    float x
    float y
    float z

cdef struct AxisSystem:
    Coordinate origin
    Coordinate x
    Coordinate y
    Coordinate z
    
cdef struct TwoAxisSystem:
    AxisSystem a
    AxisSystem b

dCoordinate0 = [('x', '<f4'), ('y', '<f4'), ('z', '<f4')]
dCoordinate = np.dtype(dCoordinate0, align=True)

dAxisSystem0 =[('origin', dCoordinate0), ('x', dCoordinate0), ('y', dCoordinate0), ('z', dCoordinate0)]
dAxisSystem = np.dtype(dAxisSystem0, align=True)

dTwoAxisSystem0 = [('a', dAxisSystem0),('b', dAxisSystem0)]
dTwoAxisSystem = np.dtype(dTwoAxisSystem0, align=True)

def print_test():
    cdef Coordinate[:] coor2
    coor = np.zeros((1), dtype=dCoordinate)
    coor["x"] = 999
    coor2 = coor
    print(coor2[0].x)
    print("success test 1")
    
    cdef AxisSystem[:] ax2
    ax = np.zeros((1), dtype=dAxisSystem)
    ax["z"] = coor
    ax2 = ax
    print(ax2[0].z.x)
    print("success test 2")
    
    cdef TwoAxisSystem[:] tax2
    tax = np.zeros((1), dtype=dTwoAxisSystem)
    tax["b"] = ax
    tax2 = tax
    print(tax2[0].b.z.x)
    print("success test 3")

<!-- Generated by Cython 0.25.2 -->
...

print_test()

999.0
success test 1
999.0
success test 2



---------------------------------------------------------------------------

ValueError                                Traceback (most recent call last)

<ipython-input-12-a9a24816d227> in <module>()
----> 1 print_test()


_cython_magic_ac12ada873519b268feb55f8cf90729a.pyx in _cython_magic_ac12ada873519b268feb55f8cf90729a.print_test (/home/sjoerd/.cache/ipython/cython/_cython_magic_ac12ada873519b268feb55f8cf90729a.c:2493)()


ValueError: Buffer dtype mismatch, expected 'Coordinate' but got 'float' in 'AxisSystem.origin'