A function that takes two forms of function call and returns their constitutent parts. The forms are syntax trees (typically given to a macro that uses the results of this function.)

1. The first form is like Module.function(1, 2, 3). In this case, the following structure is returned:

    {:in_named_module, Module, [function: 3], [1, 2, 3]}

   The module part of the function call may be multi-part, like Module.Submodule. That's what will appear in the second tuple position. The module may be the use of an alias, like alias Module.Submodule, as: S. In that case, the alias (S) will appear in the second position.

2. The second form has no module component, like function(1, 2, 3), which returns:

    {:in_calling_module, :use__MODULE__, [function: 3], [1, 2, 3]}

   This value signals that the caller must supply the module. If the caller is a macro, it will probably use __MODULE__.

Any other form will raise RuntimeError.