I tried next two variants and they are working as expected:
#proc test[T](x: T) = # this signature doesn't work. Why?!
proc test[T:not(array|seq)](x: T) =
echo x
proc test_impl[T](x: openarray[T]) =
for i in x:
echo i
proc test[T:array|seq](x: T) =
test_impl x
test(1)
test([1, 2, 3])
test([1, 2, 3, 4])
test(@[1, 2, 3])
or:
proc test[T](x: T) =
echo x
proc test_impl[T](x: openarray[T]) =
for i in x:
echo i
proc test[T](x: seq[T]) =
test_impl x
proc test[R,T](x: array[R,T]) =
test_impl x
test(1)
test([1, 2, 3])
test([1, 2, 3, 4])
test(@[1, 2, 3])
