Non-conforming complexity of Map / Set in Javascript

https://tc39.es/ecma262/multipage/keyed-collections.html#sec-map-objects says

"Maps must be implemented using either hash tables or other mechanisms that, on average, provide access times that are sublinear on the number of elements in the collection. "

However the implementation in Qt is linear, with a comment (from 2018) in qv4estable.cpp saying that it will be made faster "later".

This never happened, and it's not a nice-to-have — it's a specification requirement.