@Nullable
  private static String getSourceName(@NotNull PsiExpression source) {
    PsiReference reference = tryCast(source, PsiReference.class);
    if (reference == null) return null;
    PsiVariable variable = tryCast(reference.resolve(), PsiVariable.class);
    return variable == null ? null : variable.getName();
  }
@Nullable
  private static String getSourceName(@NotNull PsiExpression source)