stash changes before ripping up a bunch of stuff

src/process.rs

@@ -3,6 +3,7 @@ use crate::parser::*;
 use crate::spans::*;
 use crate::validator::FnInfo;
 use crate::value::Value;
+use chumsky::prelude::SimpleSpan;
 use imbl::HashMap;
 use imbl::Vector;
 use std::cell::RefCell;
@@ -35,6 +36,7 @@ pub struct Process<'src> {
     pub locals: Vec<(String, Value<'src>)>,
     pub prelude: Vec<(String, Value<'src>)>,
     pub ast: &'src Ast,
+    pub span: SimpleSpan,
     pub fn_info: std::collections::HashMap<*const Ast, FnInfo>,
 }
 
@@ -315,6 +317,11 @@ impl<'src> Process<'src> {
         }
     }
 
+    fn visit(&mut self, node: &'src Spanned<Ast>) {
+        self.ast = &node.0;
+        self.span = node.1;
+    }
+
     pub fn eval(&mut self) -> LResult<'src> {
         use Ast::*;
         let root = self.ast;