idea: interface validation

[kobi2187]

idea: interface validation

[glassesneo]

I just created an issue based on this page.

[kobi2187]

cool :-)

[glassesneo]

That's nice idea. I've been thinking about interface for a while and I was going to implement it like this:

# `interface` is a reserved word so `protocol` is used instead.
protocol IFly:
  proc fly() =
    discard

class Bird impl IFly:
  proc fly() =
    echo "I'm flying!"

and then it's converted below like nim-interface-implements:

type IFly = tuple
  fly: proc()

type Bird = ref object

proc fly(self: Bird) =
  echo "I'm flying!"

proc toProtocol(self: Bird): IFly =
  return (
    fly: self.fly()
  )

I'm interested in your idea, but I can't think of a way to implement it. Can you tell me some details?

[kobi2187]

I see. very nice. the syntax looks very clean and clear.
There is (yet) another interface implementation called iface from yglukhov.

The details need to be fleshed out. I am not sure it works.
Nim has a compiler feature to check if code compiled (checked during compile time)
https://nim-lang.github.io/Nim/system#compiles%2Cuntyped

when compiles(3 + 4):
  echo "'+' for integers is available"

so if we do:

# check_bird_fly
when not compiles(new Bird().fly()):
  {.error "fly proc not yet implemented for Bird type".}

perhaps it's a simple solution. maybe make it more explicit like:
checkImpl(Bird,IFly), then it will expand to try all the IFly defined procs for Bird.

is that clearer now? None of the code was checked, it was just an idea. see if u can get it to work... Thanks!

[glassesneo]

I see, I understand.
So the type of the first argument of checkImpl() is typed, right?
I think I can implement it well, so I'll try. Thanks!