Some sort of interface-like functionality or varargs

[Patitotective]

The following does compile though I wouldn't recommend actually using it, it 
looks like a bunch of red-flags. Maybe explicitly converting every value to a 
string is better, or if you really want to making a macro also works.
    
    
    type
      QueryParam* = tuple[key: string, value: string]
    
    proc bar*(x: (string, auto)): QueryParam =
      (x[0], $x[1])
    
    proc foo*(x: varargs[QueryParam, bar]) =
      for (key, value) in x:
        assert value is string
    
    # foo({"a": "1", "b": 2}) # This doesn't work
    foo(("a", "1"), ("b", 2))
    
    
    Run