Make Visitor/Visitable trait for mutable.

Signed-off-by: James Goppert <james.goppert@gmail.com>

Author: jgoppert

src/s2_analysis/mod.rs

@@ -1,8 +1,11 @@
 pub mod parser_helper;
 pub mod print_visitor;
 pub mod visitable;
+pub mod visitable_mut;
 pub mod visitor;
+pub mod visitor_mut;
 
 pub use parser_helper::parse_file;
 pub use print_visitor::PrintVisitor;
 pub use visitable::Visitable;
+pub use visitable_mut::VisitableMut;

src/s2_analysis/print_visitor.rs

@@ -21,7 +21,7 @@ impl Default for PrintVisitor {
     }
 }
 
-impl Visitor for PrintVisitor {
+impl Visitor<'_> for PrintVisitor {
     fn enter_any(&mut self) {
         self.level += 1;
     }