public Class<? extends GenericValue> validateTypes(final GenericValue parentExpr,
final boolean allowCollections) throws HBqlException {
final GenericValue genericValue = this.getExprArg(0);
final Class<? extends GenericValue> validatedValue = genericValue.validateTypes(this, false);
final Class<? extends GenericValue> type = this.getGenericValueClass(validatedValue);
final GenericNullCompare typedExpr;
if (TypeSupport.isParentClass(StringValue.class, type))
typedExpr = new StringNullCompare(this.isNot(), this.getExprArg(0));