[duped]

I think the majority of the convenience of structural typing can be had with explicit casting between structurally equivalent types. It eases pressure on the type checker (checking that two types are structurally equivalent is pretty quick, checking that any expression satisfies something structurally is a little harder) and gets you ultimately what a programmer wants - convenience.

[jerf]

Go's interfaces are a decent 80/20 answer. You pay for them, you opt in, and they sit on type of the base type system, they aren't the primitive the entire type system is based on and they aren't what the compiler works with at the most basic level.

I have on a number of occasions wished I could define an interface that could be fulfilled by a field without me having to write a method, but it's not a use case that comes up enough to bend a type system design around. (And there are enough other workarounds, like embedding a custom type and such that it's fine.) I think a lot of people underestimate just how large every last detail of every design decision looms at this level of a language. Too many languages doing something slightly convenient for a relatively small set of flashy use cases without fully accounting for or realizing the costs it imposes.

(This is a pretty hot take but IMHO Python is almost imploding itself constantly adding features that match that description.)

[masklinn]

> Go's interfaces are a decent 80/20 answer. You pay for them, you opt in, and they sit on type of the base type system, they aren't the primitive the entire type system is based on

That's interesting because I see them as the exact opposite. You're not saving or gaining anything of significance, and it's just increasing confusion.

Penny wise, pound foolish, if you will.

[jerf]

I'm not sure what you mean by "not gaining anything of significance." Go without interfaces (and for simplicity let's ignore 1.18's generics for a moment) would not be a useful language at any significant scale. You'd end up with a lot of "by hand" interfaces of structs full of function pointers (or method closures), only without the compiler support.

Nor am I sure exactly what "confusion" is being increased.

[masklinn]

> I'm not sure what you mean by "not gaining anything of significance." Go without interfaces (and for simplicity let's ignore 1.18's generics for a moment) would not be a useful language at any significant scale.

Why would go not have interfaces? Where did you make that up from?

Go would have nominative interfaces Like most other languages.