[Interceptor]: intercept "Method(()=> myvariable)" before the compiler generates closure

[netcorefan1]

Hello to all,
I'm able to use an interceptor like this:

Method(Func<int> delegate); // original signature
var myvar = 9;
Method(()=> myvar) // intercepted from 'MyInterceptor(Func<int> myfun) => { ... }'

The main problem is that the compiler comes first of my intercepted call and cause the generation of a closure.
I'm experimenting with source generators + interceptors in order to avoid closures automatically without recurring to a wrapper function like LambaFactory.New(param, (injectedParam) => { ... });.

In C# 12 preview features article I read this:
ASP.NET Minimal API calls like app.MapGet("/products", handler: (int? page, int? pageLength, MyDb db) => { ... }) can be intercepted to register a statically-generated thunk which calls the user’s handler directly, skipping an allocation and indirection.

Not sure If I have understood well, to me seems exactly what I'm trying to do, but I'm very confused on where I should start on.
Any help would be appreciated!
Thanks