For example, the following fails with:

import qbs
Product {
    type: Qt.core.staticBuild ? "staticlibrary" : "dynamiclibrary"
    Depends { name: "Qt.core"; requiredVersion: "5.6" }
    multiplexByQbsProperties: type.contains("foo") ? ["buildVariants"] : []
}

ERROR: /private/tmp/test.qbs:3 Can't find variable: Qt

It seems to be specific to both 'type' and 'multiplexByQbsProperties'. Replacing type with targetName in this example results in a successful build. Also, if type references Qt.core but multiplexByQbsProperties does NOT reference type, there is also no error. It's only when they're both set in this way.