Saxon

It seems to be possible to solve this by moving the static initializer of BuiltInAtomicType - the block that does

static {

    STRING.stringConverter = StringConverter.STRING_TO_STRING;

    etc

}

as static initializer of StringConverter instead. Very hard to know, though, whether this is a complete solution.

Perhaps a better solution would be to make the "constant" string converters into anonymous classes:

public final static BuiltInAtomicType HEX_BINARY =
            makeAtomicType(StandardNames.XS_HEX_BINARY, ANY_ATOMIC, true,
            new StringConverter() {
              public ConversionResult convertString(/*@NotNull*/ CharSequence input) {
                try {
                  return new HexBinaryValue(input);
                } catch (XPathException e) {
                  return new ValidationFailure(e);
                }
             };
           });