R package to extract minimal code required to reproduce a result

Question

A trivial example. Let's say this is the original code:

x = 1

y = 2

z = x * 3

If we specify that we want to reproduce z, then the package would return a new script containing only the lines of code required to generate the value z.

x = 1

z = x * 3

Does anyone know the name of a function or package that does this?