Nested stateful transformations don't work

[Tomás Capretto]

We fail at parsing and resolving terms that are nested function calls. All the following alternatives work without any problem

design_matrices("y ~ f(x1)", data)
design_matrices("y ~ f(arg = x1)", data)
design_matrices("y ~ f(arg = 'blabla')", data)
design_matrices("y ~ f(arg1= a, arg2 = "blabla")", data)

But nested function calls, like the following, don't work

design_matrices("y ~ f(g(x1))", data)
design_matrices("y ~ f(arg = g(x1))", data)
# ...etc

To solve this we need to update the Resolver.visitCallExpr() method as well as how the call term handles Expr.Call() instances, and maybe something else that I'm missing now.

[Tomás Capretto]

UPDATE

Actually, nested function calls work. But nested function calls that are stateful transformations don't work. For example, all the following work

design_matrices("y ~ np.exp(np.exp(x)))", data)
design_matrices("y ~ my_function(np.exp(x))", data)
design_matrices("y ~ scale(np.exp(x))", data) # scale() is a built-in stateful transformation

But the following does not work

design_matrices("y ~ scale(scale(x))", data)

Why would anyone do scale(scale())? Who knows... I just know that, for now, it does not work.

[Tomás Capretto]

#19