static <A> A printIndentedStructIf(bool b, A a) {
  if (b) printIndentedStruct(a);
  ret a;
}

static <A> A printIndentedStructIf(bool b, S s, A a) {
  if (b) printIndentedStruct(s, a);
  ret a;
}

static <A> A printIndentedStructIf(bool b, S s, IF0<structure_Data> makeStructureData, A a) {
  if (b)
    if (makeStructureData != null)
      printIndentedStruct(s, a, makeStructureData!);
    else
      printIndentedStruct(s, a);
      
  ret a;
}

Began life as a copy of #1027136