static @NotNull Set<AssignInstruction> getOverwrittenFields(@Nullable ControlFlow flow) {
    if (flow == null) return Set.of();
    if (!ContainerUtil.exists(flow.getInstructions(), i -> i instanceof AssignInstruction ai &&
                                                           ai.getAssignedValue() instanceof DfaVariableValue var &&
                                                           var.getPsiVariable() instanceof PsiField)) {
      return Set.of();
    }
    return new OverwrittenFieldAnalyzer(flow).getOverwrittenFields();
  }
static @NotNull Set<AssignInstruction> getOverwrittenFields(@Nullable ControlFlow flow)