mutability

Have you got a specific business problem that you've solved with and without mutability and found that the mutability made it better?

They would say internal mutability is still mutability.

Run this Mutability Detector on your code to ensure you are not allowing something to be mutable.

Small nit: you can know it's the same, unless it's a type which offers interior mutability.

But in general, exceptions can be used like an implicit Maybe/Either monad, just as mutability is an implicit IO monad.

Instead, the real prescription relies upon carefully considered/managed mutability, used with the language's intended concurrency features.

My problem is with the notion that it is the only tool and the corollary that mutability is always wrong.

And, of course, it's true that you do also have to manage the same concurrency issues as with any mutability.

Local mutability is fine, but anything that crosses method boundaries should be explicitly managed using e.g.

If you instead start with immutability, the immutability will be less of a crutch than the mutability would have been.

If you're client doesn't have mutability of obligation clause, that allows this irregardless of notice period, you probably fall under ir35.

Said perhaps more pithily: when mutable-by-default, your resultant architecture will frequently hinge on mutability.

Your use of "internal mutability" is actually a nod to moderation.

And the real "magic" is happening not through immutability alone, but careful assignment of mutability operations in conjunction with other concurrency idioms that you expect to overlay atomicity.

"If you were to design a new language today, he said, you would make it without mutable (changeable) objects, or with limited mutability."

Mutability could be always used to boost performance on Von Neumann architecture if you know what you are doing.

Every bit of code I've written before the age of Mutability-is-Pure-Evil.