From b8c7e935b637dbc756f692132a945fec423afe1c Mon Sep 17 00:00:00 2001
From: Jason Williams <936006+jasonwilliams@users.noreply.github.com>
Date: Mon, 1 Jul 2019 00:20:27 +0100
Subject: [PATCH] Update CONTRIBUTING.md

Adding debugging help
---
 CONTRIBUTING.md | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 7c1542b2db..b47078098a 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -25,6 +25,19 @@ If you don't already have Rust installed rustup is the recommended tool to use.
 
 Then simply clone this project and `cargo build`
 
+### Debugging
+
+You can see the output of tokens by adding a `dbg!(&tokens);` here:
+https://github.com/jasonwilliams/boa/blob/master/src/lib/lib.rs#L31
+
+This is useful to know if the tokens are in the right order, or any unexpected tokens are appearing.
+
+The parser's expression tree can be viewed by adding `dbg!(&expr)` here:
+https://github.com/jasonwilliams/boa/blob/master/src/lib/lib.rs#L34
+
+To get a full backtrace you will need to set the environment variable `RUST_BACKTRACE=1`
+
+
 ### Web Assembly
 
 If you want to develop on the web assembly side you can run yarn serve then go to http://localhost:8080