Saxon

When a reflexive extension function has a return type of byte[], the values are converted to XPath xs:integer instances in the range 0-255: that is, the bytes are treated as unsigned. This is not the case if the return type is simply byte or Byte. Moreover, the return values are annotated as instances of xs:byte, which is incorrect in the case of values such as 255, because these are outside the range of an xs:byte.

The problem is exposed by the extension functions saxon:hexBinary-to-octets and saxon:base64Binary-to-octets, which are implemented as reflexive extension functions with a declared return type of byte[], yet are documented to return a sequence of integers in the range 0-255. These integers are incorrectly annotated as xs:byte instances; moreover it seems the static type inferencing assumes a static type of xs:byte*.

Note there is a danger that changing the behaviour here could break existing applications.