3 ms·

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.

• 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.