anchor.diff:  	| 'interface'
   	| 'iterable'
   	| 'legacycaller'
  -	| 'legacyiterable'
   	| 'maplike'
   	| 'partial'
   	| 'required'
  
positive.code: 
  unionMemberType
  	: nonAnyType
  	| unionType typeSuffix
  	| 'any' '[' ']' typeSuffix
  ;
  
  unionMemberTypes
  
negative.code: 
  iterable
  	: 'iterable' '<' type optionalType '>' ';'
  ;
  
  optionalType
  