Dual number type

[whiterock]

I am trying to implement a dual number type in NIM, but struggling with with, 
for me, obscure error messages. Most likely I am missing something trivial, but 
after having poured in more than 2 hours in trying stuff and researching I 
still could not figure it out. Here's the minimum not working example:
    
    
    type
      Dual*[N: static[int], T: SomeFloat | Dual] = object
        real*: T
        dual*: array[N, T]
    
    proc dual*[N: static[int]; T: SomeFloat | Dual](real: T, dual: array[N, 
T]): Dual[N, T] =
      result.real = real
      result.dual = dual
    
    # scalar multiplication
    proc `*`*[N: static[int]; T: SomeFloat | Dual](x: SomeFloat; y: Dual[N, 
T]): Dual[N, T] =
      result.real = x * y.real
      for i in 0..N-1:
       result.dual[i] = x * y.dual[i]
    
    
    Run

Testing this gives different errors which I put in the comments above the 
relevant lines of code. 
    
    
    # Test
    #let a = dual[2, Dual[2, float]](
    #  dual[2, float](1.0, [0.0, 0.0]),
    #  [dual[2, float](0.0, [0.0, 0.0]), dual[2, float](1.0, [0.0, 0.0])]
    #)
    
    let a = dual(3.0, [1.0, 0.0])
    echo a # works as expected
    
    # Error: cannot instantiate 'Dual[N, T: float or float32 or float64 or 
Dual]' inside of type definition: '*'; Maybe generic arguments are missing?
    echo 183.0*a
    
    # Error: cannot instantiate: '*[2, float]'
    echo `*`[2, float](183.0, a)
    
    
    Run

Thanks in advance, ~whiterock