[jrpelkonen]

I found the arguments in this article disingenuous. First, the author complains that borrowchecker examples are toys, then proceeds to support their case with rather contrived examples themselves. For instance, the map example is not using the entry api. They’d be better served by offering up some real world examples.

[timmytokyo]

The author explained why he used contrived examples. It's because the pain arises most acutely only after your project has become large and mature but demands a small ownership-impacting change. The toy examples demonstrate the problem in the small, but they generalize to larger and more complex scenarios.

He's basically talking about the rigidity that Rust's borrow checking imposes on a program's data design. Once you've got the program following all the rules, it can be extraordinarily difficult to make even a minor change without incurring a time-consuming and painful refactor.

This is an argument about the language's ergonomics, so it seems like a fair criticism.