private static @Nullable ValueConstraint constraintFromLiteral(PsiExpression arg, boolean negate) {
    arg = PsiUtil.skipParenthesizedExprDown(arg);
    if (!(arg instanceof PsiLiteralExpression)) return null;
    Object value = ((PsiLiteralExpression)arg).getValue();
    if (value == null) return negate ? NULL_VALUE : NOT_NULL_VALUE;
    if (Boolean.TRUE.equals(value)) return negate ? TRUE_VALUE : FALSE_VALUE;
    if (Boolean.FALSE.equals(value)) return negate ? FALSE_VALUE : TRUE_VALUE;
    return null;
  }
private static @Nullable ValueConstraint constraintFromLiteral(PsiExpression arg, boolean negate)