469947 - Error in PluralForms.jsm in 3.1b2 (regarding the use of let keyword)

Status: RESOLVED DUPLICATE of bug 467747

(Core :: XPConnect, defect)

Description

[(no longer active)]

Today I updated a Fx3 profile to 3.1b2, and saw that the extension manager and download manager both turn up uninitialized, which boils down to this error in the error console:

Error: missing ; before statement
Source File: file:///C:/Program%20Files/Mozilla%20Firefox%203.1/modules/PluralForm.jsm
Line: 70
Source Code:
let gFunctions = [ 

and:

Error: missing ; before statement
Source File: file:///C:/Program%20Files/Mozilla%20Firefox%203.1/modules/DownloadUtils.jsm
Line: 76
Source Code:
let kStrings = { 

It seems that the let keyword cannot be used in a js module.

I'm not sure if it's related to bug 445873 or not, but this is serious enough to be worth filing a new bug and marking blocking-1.9.1?.

I have not seen this in other installations yet.  It happened in a clean installation to a new directory and running it on an existing Firefox 3 profile.