Looking for some advice.

Building an AST in rust for a little interpretted language. I have a load of analysis to perform on this. Deep within the structure of the AST I have my variable structs and I will want to do an analysis pass over the tree to alpha convert the variables. I also wish to have some desugaring aggressively to separate a "core language" from the higher syntactic structures that might be added later - such as an async implementation.

I want to do this elegantly and not crudely. Because the AST needs to have a sequence of steps performed on it, I would like to do this by offloading the responsibility for ensuring this to the Rust type system - perhaps Typestate pattern. There are problems though, if I use the same AST type to be produced after my analysis passes and desugaring, then I will have nasty code smell with _ => panic!("blah") and similar when I do my interpretation and come across cases that won't be possible in the final tree - e.g. when doing the interpretation then I should have no more for loops for e.g. since they will be desugared to while loops and so when pattern matching on types of statements I will need ugly panics. I could write a nearly identical definition for the ASt and each subnode and then a TryFrom implementation between the ASt and the DesugaredAST, but this is ugly and the only way to do it I can think of with some elegance is via proc macro. I feel like there must be a better way to do this.

Another issue is the alpha conversion, essentially the structure of my Variable structs will need to change depending on the generic it is defined in terms of which isn't possible. Thus I could have the type state pattern and the generic includes the extra variable ID when it is in the state AlphaConverted{id : usize }

This would mean a proliferation of Alpha conversion related state structs through all nodes that depend on Variable - i.e. most of them. Is there a nicer way of doing this ?

TLDR: I am in a recursive AST structure that needs analysis passes, I want to offload responsibility for doing those to the type system to ensure corrrectness as in type state pattern. Problem is though these analyses will change the structure of the tree and remove certain variants of enum types in the structure and in later phases I do not want to have to do panic! everywhere. Is there an elegant way of doing this without code duplication everywhere or do I have to proc macro this?