diff --git a/oden-script/src/parser.rs b/oden-script/src/parser.rs
index e05c9a84..262164f7 100644
--- a/oden-script/src/parser.rs
+++ b/oden-script/src/parser.rs
@@ -61,16 +61,18 @@ impl ExprRef {
     }
 }
 
-pub struct SyntaxTree {
+pub struct SyntaxTree<'a> {
     pub errors: Vec<SyntaxError>,
     expressions: Vec<Expr>,
+    spans: Vec<(Option<Token<'a>>, Option<Token<'a>>)>,
 }
 
-impl SyntaxTree {
+impl<'a> SyntaxTree<'a> {
     pub fn new() -> Self {
         SyntaxTree {
             errors: Vec::new(),
             expressions: Vec::new(),
+            spans: Vec::new(),
         }
     }
 
@@ -78,12 +80,27 @@ impl SyntaxTree {
         self.errors.push(error);
     }
 
-    pub fn add_expr(&mut self, expr: Expr) -> ExprRef {
+    pub fn add_expr(
+        &mut self,
+        expr: Expr,
+        start: Option<Token<'a>>,
+        end: Option<Token<'a>>,
+    ) -> ExprRef {
         let index = self.expressions.len();
         self.expressions.push(expr);
+        self.spans.push((start, end));
         ExprRef(Some(index))
     }
 
+    pub fn span(&self, expr: &ExprRef) -> (Option<Token<'a>>, Option<Token<'a>>) {
+        if let ExprRef(Some(idx)) = expr {
+            let (start, end) = &self.spans[*idx];
+            (start.clone(), end.clone())
+        } else {
+            (None, None)
+        }
+    }
+
     pub fn dump_expr(&self, expr: &ExprRef) -> String {
         match expr.0 {
             Some(idx) => {
@@ -153,7 +170,7 @@ fn token_power<'a>(token: &Option<Token<'a>>) -> Option<u8> {
 
 pub struct Parser<'a> {
     tokens: Tokens<'a>,
-    tree: SyntaxTree,
+    tree: SyntaxTree<'a>,
     current: Option<Token<'a>>,
     previous: Option<Token<'a>>,
 
@@ -173,7 +190,7 @@ impl<'a> Parser<'a> {
         parser
     }
 
-    pub fn parse(mut self) -> (SyntaxTree, ExprRef) {
+    pub fn parse(mut self) -> (SyntaxTree<'a>, ExprRef) {
         let expr = self.expression();
         self.consume(None, "expected end of expression");
         (self.tree, expr)
@@ -238,13 +255,19 @@ impl<'a> Parser<'a> {
         let token = self.previous.as_ref().unwrap();
         // What kind is it? For now let's just ... make it good.
 
-        match token.as_str().parse::<f64>() {
-            Ok(v) => self.tree.add_expr(Expr::Literal(Literal::Float64(v))),
+        let literal = match token.as_str().parse::<f64>() {
+            Ok(v) => Literal::Float64(v),
             Err(e) => {
                 self.error(format!("invalid f64: {e}"));
-                ExprRef::error()
+                return ExprRef::error();
             }
-        }
+        };
+
+        self.tree.add_expr(
+            Expr::Literal(literal),
+            Some(token.clone()),
+            Some(token.clone()),
+        )
     }
 
     fn grouping(&mut self) -> ExprRef {
@@ -257,17 +280,21 @@ impl<'a> Parser<'a> {
     }
 
     fn unary(&mut self) -> ExprRef {
-        let kind = self.previous.as_ref().unwrap().kind();
+        let token = self.previous.as_ref().unwrap().clone();
+        let kind = token.kind();
         let expr = self.expression_with_power(UNARY_POWER);
         let op = match kind {
             TokenKind::Minus => UnaryOp::Negate,
             _ => panic!("unsuitable unary: {:?}: no op", kind),
         };
-        self.tree.add_expr(Expr::Unary(op, expr))
+
+        self.tree
+            .add_expr(Expr::Unary(op, expr), Some(token), self.previous.clone())
     }
 
     fn binary(&mut self, power: u8, left: ExprRef) -> ExprRef {
-        let op = match self.previous.as_ref().unwrap().kind() {
+        let token = self.previous.as_ref().unwrap().clone();
+        let op = match token.kind() {
             TokenKind::Plus => BinaryOp::Add,
             TokenKind::Minus => BinaryOp::Subtract,
             TokenKind::Star => BinaryOp::Mutiply,
@@ -278,7 +305,11 @@ impl<'a> Parser<'a> {
         };
         let right = self.expression_with_power(power + 1);
 
-        self.tree.add_expr(Expr::Binary(op, left, right))
+        let (left_start, _) = self.tree.span(&left);
+        let (_, right_end) = self.tree.span(&right);
+
+        self.tree
+            .add_expr(Expr::Binary(op, left, right), left_start, right_end)
     }
 
     fn advance(&mut self) {