getFieldType?

I'm writing some code that is trying to pick up variable appearances (to eventually determine global variables in the code). Unfortunately, I can't rely on node.type === "Identifier" for node.name to be noted as a used reference, because Identifier is also used in other places (such as for label names). If however, I could do something like:

if (aNode.type === "identifier" && getFieldType(aNode.parent, "whatever this field was").expects(Expression))

Then I could know that this is an identifier behaving like an expression, and thus an actual candidate for a reference to a variable. If there is some other much more trivial way of figuring this out that I'm missing, I'm also happy to hear that.