diff --git a/crates/codegen/src/lib.rs b/crates/codegen/src/lib.rs
index 03ac6b5..e3f1af9 100644
--- a/crates/codegen/src/lib.rs
+++ b/crates/codegen/src/lib.rs
@@ -3,7 +3,12 @@ pub mod expr;
 pub mod statement;
 pub mod top_level;
 
-use mist_parser::ast::*;
+use std::collections::HashSet;
+
+use mist_parser::{
+    ast::*,
+    rev_mapper::{MistMap, RustMap},
+};
 
 pub struct Context {
     pub expr_ensure_semicolon: bool,
@@ -26,6 +31,8 @@ pub trait GetRust {
 pub struct RustCodegen {
     output: String,
     indent: usize,
+    mapping: HashSet<(RustMap, MistMap)>,
+    position: RustMap,
 }
 
 impl RustCodegen {
@@ -33,6 +40,8 @@ impl RustCodegen {
         Self {
             output: String::new(),
             indent: 0,
+            mapping: HashSet::new(),
+            position: RustMap(0, 0),
         }
     }
 
@@ -41,6 +50,18 @@ impl RustCodegen {
     }
 
     fn add(&mut self, s: &str) {
+        for c in s.chars() {
+            match c {
+                '\n' => {
+                    self.position.0 += 1;
+                    self.position.1 = 0;
+                }
+                _ => {
+                    self.position.1 += 1;
+                }
+            }
+        }
+
         self.output.push_str(s);
     }
 
@@ -123,21 +144,17 @@ impl GenRust for Attribute {
     }
 }
 
-impl<T: GetRust> GetRust for Spanned<T> {
-    fn get_rust(&self) -> String {
-        format!(
-            "/* {}:{} */ {}",
-            self.line,
-            self.column,
-            self.item.get_rust()
-        )
+impl<T: GetRust> GenRust for T {
+    fn gen_rust(&self, _: &mut Context, cg: &mut RustCodegen) {
+        cg.add(&self.get_rust());
     }
 }
 
 impl<T: GenRust> GenRust for Spanned<T> {
     fn gen_rust(&self, ctx: &mut Context, cg: &mut RustCodegen) {
-        cg.add_indentedln(&format!("/* {}:{} */", self.line, self.column));
-        cg.add_indented("");
+        cg.mapping
+            .insert((cg.position, MistMap(self.line, self.column)));
+
         self.item.gen_rust(ctx, cg);
     }
 }
diff --git a/crates/codegen/src/top_level.rs b/crates/codegen/src/top_level.rs
index 1af2afa..39bfbb8 100644
--- a/crates/codegen/src/top_level.rs
+++ b/crates/codegen/src/top_level.rs
@@ -195,7 +195,9 @@ impl GenRust for TopLevelKind {
                 cg.indent += 1;
 
                 for field in fields {
-                    cg.add_indentedln(&field.get_rust());
+                    cg.add_indented("");
+                    field.gen_rust(ctx, cg);
+                    cg.addln("");
                 }
 
                 cg.indent -= 1;
@@ -216,7 +218,9 @@ impl GenRust for TopLevelKind {
                 cg.indent += 1;
 
                 for field in fields {
-                    cg.add_indentedln(&(field.get_rust() + ","));
+                    cg.add_indented("");
+                    field.gen_rust(ctx, cg);
+                    cg.addln(",");
                 }
 
                 cg.indent -= 1;
diff --git a/crates/parser/src/rev_mapper/mod.rs b/crates/parser/src/rev_mapper/mod.rs
index 3e7a4d0..a251f5a 100644
--- a/crates/parser/src/rev_mapper/mod.rs
+++ b/crates/parser/src/rev_mapper/mod.rs
@@ -1,44 +1,17 @@
 use std::collections::HashSet;
 
-use pest::Parser;
-use pest_derive::Parser;
+use serde::{Deserialize, Serialize};
 
-#[derive(Parser)]
-#[grammar = "./src/rev_mapper/grammar.pest"]
-pub struct MistMapperParser;
-
-#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(
+    Debug, Default, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize,
+)]
 pub struct MistMap(pub usize, pub usize);
 
-#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(
+    Debug, Default, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize,
+)]
 pub struct RustMap(pub usize, pub usize);
 
-pub fn get_mapping(input: &str) -> HashSet<(RustMap, MistMap)> {
-    let mut mapping = HashSet::new();
-
-    let pairs = MistMapperParser::parse(Rule::mapping, input)
-        .unwrap()
-        .next()
-        .unwrap()
-        .into_inner();
-
-    for pair in pairs {
-        if pair.as_rule() == Rule::map {
-            let rs = pair.as_span().start_pos().line_col();
-            let mut inner = pair.into_inner();
-
-            let (line, col) = (
-                inner.next().unwrap().as_str().parse().unwrap(),
-                inner.next().unwrap().as_str().parse().unwrap(),
-            );
-
-            mapping.insert((RustMap(rs.0, rs.1), MistMap(line, col)));
-        }
-    }
-
-    mapping
-}
-
 pub fn find_mapping(
     mapping: &HashSet<(RustMap, MistMap)>,
     target: &RustMap,