4 ms·

Most languages would encode such behavior in a trait or a protocol instead of a zero-length struct field. It's type information and ought to be encoded in the t

Most languages would encode such behavior in a trait or a protocol instead of a zero-length struct field. It's type information and ought to be encoded in the type. From that perspective, I think it is a hack.

kbolino 2mo ago
This feels like a style complaint and not one about substance. An inaccessible (because it's named _) zero-length struct field is just another kind of metadata. It also doesn't require you to pollute the method set, which would be a bigger issue. The real hack to me is that anything which simply has Lock() and Unlock() methods is considered uncopyable.
- reorder9695 2mo ago
  Coming from Rust anyway (can't say I'm familiar with Go), nothing about having it as a trait would pollute the method set, traits don't have to have methods (e.g. pin, unpin, send, sync, etc.). Yes a zero length field can be metadata and this is a style complaint but a struct's fields are traditionally its data and the type is its metadata, I feel like it's harmful to mix these two as I at least wouldn't generally look at fields to find metadata for the struct.
  - kbolino 2mo ago
    Interfaces in Go (the closest equivalent to traits in Rust) don't have to have methods either, but they are structurally typed. This is like "static duck typing" if you will. So an interface with no methods is implemented by every type in the language (indeed, this became such a useful pattern that the name "any" was reserved for it in Go 1.18). Marker interfaces can exist in Go, but here they are another kind of hack. They must define at least one method (which doesn't have to be public), though that method is never actually meant to be called.
  - woadwarrior01 2mo ago
    I'm only peripherally familiar with Go. IIRC, Rust defaults to move-only structs with the option to make them copyable with the Copy trait. Swift defaults to copyable structs (like Go), but has a ~Copyable generic type constraint to make them move-only.
  - rcxdude 2mo ago
    Rust has similar zero-sized-types, probably the most 'magical' being PhantomData.
- zimpenfish 2mo ago
  > The real hack to me is that anything which simply has Lock() and Unlock() methods is considered uncopyable. It's a shame they made them generic, taking no arguments and returning nothing; if they'd gone for `Lock(sync.LockType)` or something like that, it would be more difficult to accidentally trigger the `noCopy` flag.
stevecoalbear 2mo ago
Go's entire schtick is being simple, eschewing language complexity in favour of letting the programmer handle it themself. Like C, but with pointer safety and garbage collection. We learned from C++ and Rust that languages can be so smart that people can't effectively use them. Go is the opposite. It's so dumb that anyone can use it, but it doesn't have some native language features you might want.
- insanitybit 2mo ago
  How is this simple? It's basically a hint to `go vet` that uses a special interface pattern. I'm baffled by what some people call "simple" lol
  - a2ff6eeb0 2mo ago
    How much additional complexity do users need to be aware of when writing new code because of the way this was implemented? Adding new features makes the language bigger, for something that Claude tells me is used 20 times in total in the entire Go codebase.
    - insanitybit 2mo ago
      I don't know the answer to those things, it feels like it's sort of on the one saying "This is simple" to explain why.
      - a2ff6eeb0 2mo ago
        Because it doesn't expand the language and force the user to learn new features, it instead puts the ugliness deep in the library where nobody needs to interact with it.
        insanitybit 2mo ago
        This explicitly leverages a hidden "feature" of the language, which is how Sync impacts copying (rather unintuively). It leverages this to create an interface based on that hidden feature to create a marker that is consumed by a specific tool (not the compiler). This feels like at least two layers of special behaviors.
Boxxed 2mo ago
Soooo like a PhantomData in Rust?

kbolino 2mo ago

This feels like a style complaint and not one about substance. An inaccessible (because it's named _) zero-length struct field is just another kind of metadata. It also doesn't require you to pollute the method set, which would be a bigger issue. The real hack to me is that anything which simply has Lock() and Unlock() methods is considered uncopyable.

reorder9695 2mo ago
Coming from Rust anyway (can't say I'm familiar with Go), nothing about having it as a trait would pollute the method set, traits don't have to have methods (e.g. pin, unpin, send, sync, etc.). Yes a zero length field can be metadata and this is a style complaint but a struct's fields are traditionally its data and the type is its metadata, I feel like it's harmful to mix these two as I at least wouldn't generally look at fields to find metadata for the struct.
- kbolino 2mo ago
  Interfaces in Go (the closest equivalent to traits in Rust) don't have to have methods either, but they are structurally typed. This is like "static duck typing" if you will. So an interface with no methods is implemented by every type in the language (indeed, this became such a useful pattern that the name "any" was reserved for it in Go 1.18). Marker interfaces can exist in Go, but here they are another kind of hack. They must define at least one method (which doesn't have to be public), though that method is never actually meant to be called.
- woadwarrior01 2mo ago
  I'm only peripherally familiar with Go. IIRC, Rust defaults to move-only structs with the option to make them copyable with the Copy trait. Swift defaults to copyable structs (like Go), but has a ~Copyable generic type constraint to make them move-only.
- rcxdude 2mo ago
  Rust has similar zero-sized-types, probably the most 'magical' being PhantomData.
zimpenfish 2mo ago
> The real hack to me is that anything which simply has Lock() and Unlock() methods is considered uncopyable. It's a shame they made them generic, taking no arguments and returning nothing; if they'd gone for `Lock(sync.LockType)` or something like that, it would be more difficult to accidentally trigger the `noCopy` flag.

stevecoalbear 2mo ago

Go's entire schtick is being simple, eschewing language complexity in favour of letting the programmer handle it themself. Like C, but with pointer safety and garbage collection. We learned from C++ and Rust that languages can be so smart that people can't effectively use them. Go is the opposite. It's so dumb that anyone can use it, but it doesn't have some native language features you might want.

insanitybit 2mo ago
How is this simple? It's basically a hint to `go vet` that uses a special interface pattern. I'm baffled by what some people call "simple" lol
- a2ff6eeb0 2mo ago
  How much additional complexity do users need to be aware of when writing new code because of the way this was implemented? Adding new features makes the language bigger, for something that Claude tells me is used 20 times in total in the entire Go codebase.
  - insanitybit 2mo ago
    I don't know the answer to those things, it feels like it's sort of on the one saying "This is simple" to explain why.
    - a2ff6eeb0 2mo ago
      Because it doesn't expand the language and force the user to learn new features, it instead puts the ugliness deep in the library where nobody needs to interact with it.
      - insanitybit 2mo ago
        This explicitly leverages a hidden "feature" of the language, which is how Sync impacts copying (rather unintuively). It leverages this to create an interface based on that hidden feature to create a marker that is consumed by a specific tool (not the compiler). This feels like at least two layers of special behaviors.

Boxxed 2mo ago

Soooo like a PhantomData in Rust?