In general you can't in a maintainable way for non-trivial local functions (reason explained in a comment to this response). A local function that uses variables of the method where it is defined (so a non-trivial one, ones that don't use local variables could be private methods) has a special parameter containing these variables. You can't easily recreate this parameter → you can't call it.
It can be easily seen in TryRoslyn (how much I love TryRoslyn! I use it very often
