"Impossible" errors

[ndw]

I'm using this issue to track errors that are in the specification(s) but are unlikely to be raised. I'm not sure we need to do anything about them, but the test suite reports how many tests we have for error conditions. If an error is never raised, then that's a little misleading with respect to coverage...

[ndw]

err:XS010, a pipeline contains a step whose specified inputs, outputs, and options do not match the for steps of that type

We have more specific error codes for each of those conditions.

[ndw]

err:XS0027, It is a static error if an option is specified with both the shortcut form and the long form.

I guess this one isn't impossible, but I think it's subsumed by err:XS0080, it is a static error to include more than one p:with-option with the same option name as part of the same step invocation.

My implementation transforms shortcut options into "regular" options, so I always get err:XS0080.

[xml-project]

1. My implementation raises XS0010 only for a p:viewport with more than one p:output, but I guess XS0100 would be ok too.
2. I think XS0027 might be more helpful, but my implementation does the same as yours.

[ndw]

err:XS0048, It is a static error to use a declared step (an extension step without a body) as a compound step

I throw XS0100 because I know what all the compound steps are and I reject the attempt to construct the invalid compound step long before I look at whether or not the wrapper is declared as an atomic, extension step.