private static @Nullable PsiVariable resolveSimpleVariableReference(@NotNull PsiReferenceExpression expression) {
    final PsiExpression qualifierExpression = expression.getQualifierExpression();
    if (qualifierExpression == null ||
        qualifierExpression instanceof PsiThisExpression ||
        qualifierExpression instanceof PsiSuperExpression) {
      final PsiElement resolved = expression.resolve();
      return resolved instanceof PsiVariable ? (PsiVariable)resolved : null;
    }
    return null;
  }
private static @Nullable PsiVariable resolveSimpleVariableReference(@NotNull PsiReferenceExpression expression)