From 35bf004cc923c1bd61a75fa0ff9b336644f0c8b0 Mon Sep 17 00:00:00 2001
From: David Li <li.davidm96@gmail.com>
Date: Sat, 4 Nov 2017 08:34:52 -0400
Subject: Add location information to AST

---
 src/ast.rs        | 24 +++++++++++++++++++++++-
 src/taiga.lalrpop | 12 ++++++++----
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/src/ast.rs b/src/ast.rs
index b5f2049..3863ce9 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -1,5 +1,27 @@
 #[derive(Debug)]
-pub struct Program(pub Box<Expression>);
+pub struct WithLocation<T> {
+    value: T,
+    location: (usize, usize),
+}
+
+impl<T> WithLocation<T> {
+    pub fn new(value: T, start: usize, end: usize) -> WithLocation<T> {
+        WithLocation {
+            value: value,
+            location: (start, end),
+        }
+    }
+
+    pub fn map<U, F: FnOnce(T) -> U>(self, f: F) -> WithLocation<U> {
+        WithLocation {
+            value: f(self.value),
+            location: self.location,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Program(pub Box<WithLocation<Expression>>);
 
 #[derive(Debug)]
 pub enum Expression {
diff --git a/src/taiga.lalrpop b/src/taiga.lalrpop
index b60d68f..08c3cd3 100644
--- a/src/taiga.lalrpop
+++ b/src/taiga.lalrpop
@@ -1,5 +1,5 @@
 use std::str::FromStr;
-use ast;
+use ast::{self, WithLocation};
 
 grammar;
 
@@ -7,8 +7,12 @@ pub Program: ast::Program = {
     Expression => ast::Program(<>),
 };
 
-Expression: Box<ast::Expression> = {
-    Num => Box::new(ast::Expression::Number(<>)),
+Expression: Box<ast::WithLocation<ast::Expression>> = {
+    Num => Box::new(<>.map(|v| ast::Expression::Number(v))),
 };
 
-Num: u64 = r"[0-9]+" => u64::from_str(<>).unwrap();
+Num: WithLocation<u64> = <e: Spanned<r"[0-9]+">> => e.map(|v| u64::from_str(v).unwrap());
+
+Spanned<T>: WithLocation<T> = {
+    <l: @L> <v: T> <r: @R> => WithLocation::new(v, l, r)
+};
-- 
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