[copascetic]

I think the request is rather justified given your response, which is engaging with a strawman version of the thesis presented in the post. What you wrote about the virtues of newtype was explained quite well in the post itself, but you seem to want to disagree about something. You present another strawman in this reply:

> the claim that newtype-based approaches are not type safety

To use your phrasing, the claim is that newtypes do not in and of themselves provide type safety, but that "newtype-based approaches" can and do provide a weaker form of safety than constructive modeling. Further, it's important to understand what the critical additional steps are in such approaches to achieving that safety and avoid cargo-culting "newtypes make things type-safe", and to understand the ways this safety can be violated.

[lmm]

> What you wrote about the virtues of newtype was explained quite well in the post itself

The post implied that the newtype-based approach was somehow "not type safety" and offered significantly less safety in practice than the constructive model approach. The first of those is definitely false, and based on my own experiences I don't believe the second.

> Further, it's important to understand what the critical additional steps are in such approaches to achieving that safety and avoid cargo-culting "newtypes make things type-safe", and to understand the ways this safety can be violated.

Naively it sounds like that would be important, but I'm not convinced it actually is in practice. My experience is that even a cargo-culty use of newtypes delivers most (maybe even all) of the defect rate benefit, and that these vigorous warnings about newtypes are more likely to reduce real-world safety (because people faced with cases that they can't produce a constructive model for will be encouraged to use an alias, or no type at all, rather than a newtype) than improve it.

[copascetic]

Again, you are conflating newtypes per se with approaches using newtype as part of an overall abstraction and interface design including constructor hiding. The post makes this quite clear and the author and others have pointed out this distinction to you multiple times here. Just because you made an inference and argued against it doesn't mean the article was making such an implication.

Your second point is certainly arguable and does represent a substantive disagreement with the post unlike your first comment. I think the post makes a solid case that gratuitous use of newtype absent any abstraction boundary is an anti-pattern that provides little benefit if conversions are done ad hoc. Sprinkling on some newtype can certainly help some cases, but the post encourages critical thinking about these issues and explores where this reasoning falls down. If your claim is that critical thinking gets in the way of cargo-culting approaches that lead to "nominal" type safety then you would be right. Your last parenthetical doesn't seem like a reasonable response of someone who has read and understood this post. The post specifically encourages the use of newtype with abstraction boundaries where practical and works through an example.

[lmm]

> Again, you are conflating newtypes per se with approaches using newtype as part of an overall abstraction and interface design including constructor hiding. The post makes this quite clear and the author and others have pointed out this distinction to you multiple times here. Just because you made an inference and argued against it doesn't mean the article was making such an implication.

The author is still carefully avoiding describing any newtype-based approach as "type safety", to the point that they would mislead anyone who wasn't already familiar with the subject.

> Your last parenthetical doesn't seem like a reasonable response of someone who has read and understood this post. The post specifically encourages the use of newtype with abstraction boundaries where practical and works through an example.

It works through an example and follows that with a long list of (IMO exaggerated) weaknesses of that example, which seems more designed to dismiss it. It does not "specifically encourage" using newtypes at all (indeed it says "if you are fond of newtypes" as though one would only ever use newtypes for private emotional reasons). It concludes with "correctness by construction should be preferred whenever practical".

[copascetic]

If you'd carefully reread the post you'll see that your first assertion is false. It contains this sentence: "But it is a meaningfully distinct kind of type safety from the one I highlighted a year ago, one that is far weaker." The antecedent of "one" is "type safety", which is being provided, just, weaker, not "not type safety" as you claim.

As for whether the example is being "dismissed" or not, I also think that's manifestly false. See: "[this tradeoff] is often a very good one!" while still diving into exactly what the tradeoff is.