From bd0024a9c263fa3684e1e433dabb65644519583b Mon Sep 17 00:00:00 2001
From: Alan Pierce <alangpierce@gmail.com>
Date: Wed, 27 Jul 2016 23:16:30 -0700
Subject: [PATCH] Fix incorrect location data in OUTDENT nodes

In f609036beef3aa1529c210ffad3ced818ee94cce, a line was changed from
`if length > 0 then (length - 1) else 0` to `Math.max 0, length - 1`. However,
in some cases, the `length` variable can be `undefined`. The previous code would
correctly compute `lastCharacter` as 0, but the new code would compute it as
`NaN`. This would cause trouble later on: the end location would just be the end
of the current chunk, which would be incorrect.

Here's a specific case where the parser was behaving incorrectly:
```
a {
  b: ->
    return c d,
      if e
        f
}
g
```

The OUTDENT tokens after the `f` had an undefined length, so the `NaN` made it
so the end location was at the end of the file. That meant that various nodes in
the AST, like the `return` node, would incorrectly have an end location at the
end of the file.

To fix, I just reverted the change to that particular line.
---
 lib/coffee-script/lexer.js | 2 +-
 src/lexer.coffee           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/coffee-script/lexer.js b/lib/coffee-script/lexer.js
index 21e5ac20..250f1037 100644
--- a/lib/coffee-script/lexer.js
+++ b/lib/coffee-script/lexer.js
@@ -768,7 +768,7 @@
       }
       locationData = {};
       ref2 = this.getLineAndColumnFromChunk(offsetInChunk), locationData.first_line = ref2[0], locationData.first_column = ref2[1];
-      lastCharacter = Math.max(0, length - 1);
+      lastCharacter = length > 0 ? length - 1 : 0;
       ref3 = this.getLineAndColumnFromChunk(offsetInChunk + lastCharacter), locationData.last_line = ref3[0], locationData.last_column = ref3[1];
       token = [tag, value, locationData];
       return token;
diff --git a/src/lexer.coffee b/src/lexer.coffee
index 2e6090df..83f9f907 100644
--- a/src/lexer.coffee
+++ b/src/lexer.coffee
@@ -658,7 +658,7 @@ exports.Lexer = class Lexer
 
     # Use length - 1 for the final offset - we're supplying the last_line and the last_column,
     # so if last_column == first_column, then we're looking at a character of length 1.
-    lastCharacter = Math.max 0, length - 1
+    lastCharacter = if length > 0 then (length - 1) else 0
     [locationData.last_line, locationData.last_column] =
       @getLineAndColumnFromChunk offsetInChunk + lastCharacter