mbeckerle commented on code in PR #1137:
URL: https://github.com/apache/daffodil/pull/1137#discussion_r1446526490
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daffodil-core/src/main/scala/org/apache/daffodil/core/dpath/Expression.scala:
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@@ -2295,6 +2295,18 @@ abstract class FunctionCallBase(
res
}
+ final def checkArgArray(): Unit = {
+ lazy val isArray = expressions.head match {
+ case rpe: RelativePathExpression => rpe.steps.last.isArray
+ case rpe: RootPathExpression => rpe.steps.last.isArray
+ case _ => true
Review Comment:
> One thing to consider is this doesn't catch expressions like this:
>
> ```xq
> fn:count(if (some_condition) then /some/path else /some/other/path)
> ```
>
> I think that's legal and I think would be considered invalid because of
this case.
>
> I'm not sure if there's a good way to check that all branches of a
subexpression result in an array. We must be able to get some basic information
since we can statically check that all branches have the same type. I think we
do that via `inherentType`, but I'm not sure the result would return
information about being an array or not. Maybe this is just a limitation of our
checking and it's good enough? And if someone whats the above, they would need
to do something like this:
>
> ```xq
> if (some_condition) then fn:count(/some/path) else
fn:count(/some/other/path)
> ```
Pretty sure the expression type system treats "array or optional" as a type,
and so the type inference on the expressions requires all branches of an IF to
evaluate to an array/optional in order to satisfy the requirements of fn:count.
It's supposed to propagate the requirement from the fn:count into the
expression, which would then propagate it to the then and else branch
expressions as the "target type" that the expression is trying to create.
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