Steps to Reproduce:
At https://th.wikipedia.org/wiki/Special:Abusefilter/test, paste the following code:
a := []; a[] := 0
and then click the "Test" button
Actual Results:
An internal error occurs:
[XbkMfApAICoAAHOmRuQAAAAL] 2019-10-30 04:07:24: การยกเว้นข้อผิดพลาดร้ายแรงของประเภท "TypeError"
Expected Results:
I think the semantics of <e1>[] := <e2> should be, mutating <e1> to append <e2>, and the whole expression evaluates to <e2>.