Make interface implementation explicit

[RednibCoding]

As in go, v does not require to explicitly write that a struct/class implements an interface. This is one of the worst design decisions the go team made. In a big project, it is hard to track down in the code what interface a struct implements. Code readability gets worse with this decision.
Also, implementing an interface in other languages also kind of acts as a contract that a struct/class has these methods, and the ide will warn you if not, which is really nice.

Almost all of the developers I know that use go, dont like that design decision.

Please introduce a keyword "implements" or some kind of syntax that makes this explicit.

[JalonSolov]

Not every developer thinks it's a bad way of doing things. And "implements" seems too... "OOPy".

However, that's what discussions are for.

[RednibCoding]

I mean what means oopy? Either a struct implements an interface or not. Making it explicit by saying "implements" does not change the "oopness". :)
But it makes the code a lot more readable because you don't have to guess what interface a struct implements.
Code readability is, when you can read code like a book, from top to bottom and understand the behavior. If you have to jump back and forth a lot, that's a bad sign.

Would be nice if this is at least optional.

[ghost]

I really like the interface specs of Go and V.
It is very convenient because I don't have to design the Interface first and then implement Classes accordingly like in Java.

On the other hand, I agree that readability is bad.
But that's the same problem that Generics has.
If we are discussing good readability, I think generics should be treated together.

My opinion is that this inconvenience should be compensated for by the IDE, not by the language specification.

[ghost]

Have you ever used the "just in time" interface?

[ghost]

The Go interface is fundamentally different from Java and other interfaces.
I think it would be better to change the name of the interface to "interface" to better recognize the role of Go's interface.
Not giving structs keywords such as implement is what makes Go's Interface so useful.
I think it is very useful once you understand how to use it.
It is fundamentally impossible to give the keyword "implement" to struct.

[ghost]

Nevertheless, the problem of readability still remains.
Are you absolutely certain that LS cannot solve this?
Are you involved in the development of LS?
I am not involved, so I don't know for sure.

[ghost]

The compiler throws an error when actually used.

struct SFoo{}

interface Foo{
	get()
}

fn main(){
	sf := SFoo{}
	mut arr := []Foo{}
	arr << sf
}

bug.v:10:9: error: `SFoo` doesn't implement method `get` of interface `Foo`
    8 |     sf := SFoo{}
    9 |     mut arr := []Foo{}
   10 |     arr << sf
      |            ~~
   11 | }

[RednibCoding]

Yes this throws an error because arrays in v are homogeneous and SFoo is basically a different type. Same probably happens when you are trying to cast.
But by the time your write the implementation of the struct, the compiler/language server can't know.
I don't know how hard it would be to implement such keyword I've never written any compiler. Just a few simple dsl's (interpreted, not compiled).
But i understand your standpoint.

[spytheman]

This was implemented in #22214 and available in https://github.com/vlang/v/releases/tag/0.4.8 .

[JalonSolov]

Documented under https://docs.vlang.io/type-declarations.html#implement-an-interface