Arrays of an interface

[Abdulhaq]

Sorry to reply to me own post so quickly, a clue (it seems to me) 
is this part of the error:

smidgen/ast/klass.d(15): Error: size of type Method is not known

Line 15 is where I import the interface:
import smidgen.ast.method: Method, MethodImpl, Visibility, SMID;

and in the relevant file,

interface Method: ConverterManagerProvider {
	bool virtual();
	bool abstract_();
	bool static_();
	bool constructor();
	bool destructor();
	bool hasEllipsis();
	bool const_();
	bool transferBack();
etc...
	

Well, interfaces don't have sizes, do they? So does [] only 
really work for classes?