[plt-scheme] variable or syntactic binding

Examining an id-stx in syntax-case, is it possible to find out if it has a variable binding or a syntactic binding? I have not found any info on this in the docs. I have tried procedures identifier-binding and identifier-transformer-binding. The former returns a true value for an id-stx with a syntactic binding. The latter returns false for such an id-stx. The expander does have to know the difference, I suppose.
Thanks, Jos
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