I’m back to continue work on the gsoc! Today I changed the syntax for fused types according to the discussion on the mailing list. You can now write
cdef fused my_fused_type:
my_fused_type = cython.fused_type(int, float, ...)
in pure mode. The plan then is to merge the current fused function on top of Vitja's work on the new CyFunction. Until that is merged I'll try to support fused types as part of def functions and not just as part of cdef or cpdef functions.