error message missing invalid type of the key

[Matthias Brantner]

The following index declaration results in an error message that is missing the invalid type of the key.

Declaration:

declare %an:automatic %an:value-equality index foo:index
  on nodes dml:collection(xs:QName("foo:coll"))
  by string(@id);

Error message:

[zerr:ZDST0027]: "foo:index": index bad key type

It would be nice to get something as follows:

"foo:index": index bad key type (xs:untypedAtomic)

or maybe even that the type declaration cannot be omitted for value indices.