How to upper case a experssion in declarative marco?

#1

I want to upper case some experssion $x (or do any other process on it).
How to write this?

And where is the sheet of the suffixes? (like ident, expr for $x)

Thank you

#2

I don’t think it’s possible to do lexical transformations like uppercase.

The designators are listed here: https://doc.rust-lang.org/nightly/reference/macros-by-example.html