Pxd support of fused types

[thautwarm]

Currently, while

from cython cimport fused_type
cdef fused Num:
   int
   float
cpdef num_func(Num x)

produces a Cython compiler error, and follow codes can be a workaround:

from cython cimport fused_type
Num = fused_type(int, float)
cpdef num_func(Num x)

Post it here for it could be helpful for many, and no doubt can be regarded as a bug.

[will-ca]

Under language_level 3 with language "c++", I've been able to define fused types in the .pxd file just fine, without having even having a from cython cimport fused_type statement.

[scoder]

I cannot reproduce this.

test.pyx:

cpdef num_func(Num x): return

test.pxd:

from cython cimport fused_type  # unused code, can be deleted
cdef fused Num:
   int
   float
cpdef num_func(Num x)