Machinery for hygienic macros, inspired by the
 Matthew Flatt, Ryan Culpepper, David Darais, and Robert Bruce Findler. 2012.
Macros that work together: Compile-time bindings, partial expansion,
and definition contexts. J. Funct. Program. 22, 2 (March 2012), 181-216.
Extra information for tracking spans of macro and syntax sugar expansion
A mark is a unique ID associated with a macro expansion.
A SyntaxContext represents a chain of macro expansions (represented by marks).
The kind of compiler desugaring.
The source of expansion.
A property of a macro expansion that determines how identifiers produced by that expansion are resolved.