[randomdata]

There is no such requirement. Common wisdom suggests that you should ensure zero values are useful, but that isn't about every random struct field – only the values you actually give others. Initialize your struct fields and you won't have to consider their zero state. They will never be zero.

It's funny seeing this beside the DRY thread. Seems programmers taking things a bit too literally is a common theme.

[stouset]

> Initialize your struct fields and you won't have to consider their zero state.

“Just do the right thing everywhere and you don’t have to worry!”

You can’t stop consumers of your libraries from creating zero-valued instances.

[randomdata]

Then the zero value is their problem, not yours. You have no reason to be worried about that any more than you are worried about them not getting enough sleep, or eating unhealthy food. What are you doing to stop them from doing that? Nothing, of course. Not your problem.

Coq exists if you really feel you need a complete type system. But there is probably good reason why almost nobody uses it.

[stouset]

> Then the zero value is their problem, not yours.

Except for all those times you're the consumer of someone else's library and there's no way for them to indicate that creating a zero-valued struct is a bug.

Again, it's the philosophy of "Just do the right thing everywhere and you don’t have to worry!" Sometimes it's nice to work with a type system where designers of libraries can actually prevent you from writing bugs.

[randomdata]

> Except for all those times you're the consumer of someone else's library and there's no way for them to indicate that creating a zero-valued struct is a bug.

Nonsense. Go has a built-in facility for documentation to communicate these things to other developers. Idiomatic Go strongly encourages you to use it. Consumers of the libraries expect it.

> Sometimes it's nice to work with a type system where designers of libraries can actually prevent you from writing bugs.

Well, sure. But, like I said, almost nobody uses Coq. The vast, vast, vast majority of projects – and I expect 100% of web projects – use languages with incomplete type systems, making what you seek impossible.

And there's probably a good reason for that. While complete type systems sound nice in theory, practice isn't so kind. There are tradeoffs abound. There is no free lunch in life. Sorry.

[owl57]

> The vast, vast, vast majority of projects – and I expect 100% of web projects – use languages with incomplete type systems, making what you seek impossible.

…where, "what GP seeks" is…

> way for [library authors] to indicate that creating a zero-valued struct is a bug

I'd say that's a really low and practical bar, you really don't need Coq for that. Good old Python is enough, even without linters and type hints.

Of course it's very easy to create an equivalent of zero struct (object without __init__ called), but do you think it's possible to do it while not noticing that you are doing something unusual?

[randomdata]

> Good old Python is enough

No, Python is not enough to "...work with a type system where designers of libraries can actually prevent you from writing bugs." Not even typed Python is going to enable that. Only a complete type system can see the types prevent you from writing those bugs. And I expect exactly nobody is writing HTTP services with a language that has a complete type system – for good reason.

> Of course it's very easy to create an equivalent of zero struct

Yes, you are quite right that you, the library consumer, can Foo.__new__(Foo) and get an object that hasn't had its members initialized just like you can in Go. But unless the library author has specifically called attention to you to initialize the value this way, that little tingling sensation should be telling you that you're doing something wrong. It is not conventional for libraries to have those semantics. Not in Python, not in Go.

Just because you can doesn't mean you should.

[the_gipsy]

You don't have to go as far as Coq. Rust manages "parse, don't validate" extremely well with serde.

Go's zero-values are the problem, not any other lack of its type system.

[randomdata]

> You don't have to go as far as Coq.

No, you do. Anywhere the type system is incomplete means that the consumer can do something the library didn't intend. Rust does not have a complete type system. There was no relevance to mentioning it. But I know it is time for Rust's regularly scheduled ad break. And while you are at it, enjoy a cool, refreshing Coca-Cola.

> Go's zero-values are the problem

"Sometimes it's nice to work with a type system where designers of libraries can actually prevent you from writing bugs." has nothing to do with zero-values. It doesn't even really have anything to do with Go specifically. My, the quality of advertising has really declined around here. Used to be the Rust ads at least tried to look like they fit in.

[DandyDev]

You manage to present a strawman and produce a No True Scotsman fallacy all at once in this comment thread.

Nobody is suggesting that Coq should be used, so stop bringing it up (strawman). And yes, Coq might have an even stricter and more expressive type system than Rust. But nobody is asking for a perfect type system (no true Scotsman). People are asking to be able to prevent users of your library to provide illegal values. Rust (and Haskell and Scala and Typescript and ….) lets you do this just fine whereas Golang doesn’t.

And personally I would much rather have the compiler or IDE tell me I’m doing something wrong than having to read the docs in detail to understand all the footguns.

My personal opinion is that - even though I’m very productive with Golang and I enjoy using it - Golang has a piss poor type system, even with the addition of Generics.

[randomdata]

> People are asking to be able to prevent users of your library to provide illegal values. [...] and Typescript

Typescript, you say?

   const bar: Foo = {} as Foo

Hmm. Oh, right, just don't hold it wrong. But "sometimes it's nice to work with a type system where designers of libraries can actually prevent you from writing bugs."

Your example doesn’t even satisfy the base case, let alone the general case. Get back to us when you have actually read the thread and can provide something on topic.