LeftHandSideExpression of Assignment Expression can be a MemberExpression as well.

[skepticfx]

I feel there is a small bug when walking the AST for AssignmentExpression, where the LeftHandSideExpression can be a MemberExpression as well in addition to Pattern.

Currently, the code only considers the Pattern type: https://github.com/estools/escope/blob/master/src/referencer.js#L460

Hence, a valid MemberExpression assignment like,

document.cookie = "key=value";

would not be stored as a proper WriteExpr in the Reference object. Rather there would be one referenece for document with a Flag of 1(READ).

Such assignment expressions are alteast very common in browser JavaScript code and a fix would be great. I know the code also, references something similar in the comments: https://github.com/estools/escope/blob/master/src/referencer.js#L98

If its considered a bug, any tips on how to fix this would be greatly appreciated, since I can work on a PR.

[mysticatea]

This is a not bug.
Currently, escope does not support property references.

document.cookie = "key=value";

In this case, a reading reference of document is needed. It's correct. If document is null, we see a null reference access error.
If there is a writing property reference of document.cookie additionally, it's very useful.

However, it probably is a breaking change.

Related: #41

[skepticfx]

I see! Thanks for the explanation. Appreciate it!