In the past one could write the typedesc parameter as generic notation. This seems not to work anymore.
# typedesc parameter
proc unit(t: typedesc[int]): t = 0
proc unit(t: typedesc[string]): t = ""
proc unit(t: typedesc[float]): t = 0.0
assert unit(int) == 0
assert unit(string) == ""
assert unit(float) == 0.0
# following seems not to work (anymore?)
assert unit[int]() == 0
assert unit[string]() == 0
assert unit[float]() == 0
@Araq said this should still work, therefor I wrote this report :)