Constraints over anonymous variables are not parsed

[wouterwln]

Let's say we have the following example:

@model function test_model(a, b, c)
    x ~ Gamma(b = b, c = sqrt(c))
    a ~ Normal(x, 1)
end

we cannot specify any constraint around this Gamma node since in the internal representation c is not connected to it (c is connected to a sqrt node, which spawns an anonymous variable that is actually connected to the Gamma node. I currently also have no inspiration on how to solve this efficiently. Probably after refactoring the constraints to a more efficient algorithm a path will open.

[wouterwln]

@bvdmitri this can be closed, right?