How to add a UDF with variable number parameter in calcite?

Question

I'm using Apache Calcite to validate SQL. I add tables and UDFs dynamically. The problem is when I add a UDF with variable number parameter, the validator can not find this function.

Version of Calcite is 1.18.0

And this is my code.

TestfuncFunction.java

public class TestfuncFunction {
    public String testfunc(String... arg0) {
        return null;
    }
}

Add UDF

Function schemafunction = ScalarFunctionImpl.create(TestfuncFunction.class),"testfunc");
SchemaPlus schemaPlus = Frameworks.createRootSchema(true);
schemaPlus.add("testfunc", schemafunction);

SQL

select testfunc(field1, field2) from test_table

testfunc is a ScalarFunction with variable number parameter,field1 and field2 are columns of test_table. So this is a legal SQL. But I got this CalciteContextException when validating:

No match found for function signature testfunc(<CHARACTER>, <CHARACTER>)

I tryed to change my sql into one parameter like this:

select testfunc(field1) from test_table

and got this exception

java.lang.AssertionError: No assign rules for OTHER defined
    at org.apache.calcite.sql.type.SqlTypeAssignmentRules.canCastFrom(SqlTypeAssignmentRules.java:386)
    at org.apache.calcite.sql.type.SqlTypeUtil.canCastFrom(SqlTypeUtil.java:864)
    at org.apache.calcite.sql.SqlUtil.lambda$filterRoutinesByParameterType$4(SqlUtil.java:554)
    ...

It seems that calcite transform java array type into SqlTypeName.OTHER. I have tryed to override method "createJavaType" in JavaTypeFactoryImpl like this:

private static class CustomJavaTypeFactoryImpl extends JavaTypeFactoryImpl {
    @Override
    public RelDataType createJavaType(Class clazz) {
        if (clazz.isArray()) {
            return new ArraySqlType(super.createJavaType(clazz.getComponentType()), true);
        }
        return super.createJavaType(clazz);
    }
}

but it did not work.

Do Calcite support UDF with variable number parameter, and what should I do.