[next] self cannot be constrained by an interface

[Frityet]

local interface ISoundMaker
    makesound: function(ISoundMaker)
end

local record Animal is ISoundMaker
    species: string
end

function Animal:create(species: string): Animal
    return setmetatable({ species = species }, { __index = Animal })
end

function Animal:makesound()
    print("Animal sound")
end

local record Person is ISoundMaker
    name: string
end

function Person:create(name: string): Person
    return setmetatable({ name = name }, { __index = Person })
end

function Person:makesound()
    print("Person sound")
end

local things: {ISoundMaker} = {
    Animal:create("Dog"),
    Person:create("John")
}

for _, thing in ipairs(things) do
    thing:makesound()
end

Fails with:

========================================
2 errors:
test.tl:14:1: type signature of 'makesound' does not match its declaration in Animal: argument 0: Animal is not a ISoundMaker
test.tl:26:1: type signature of 'makesound' does not match its declaration in Person: argument 0: Person is not a ISoundMaker
----------------------------------------
2 errors

[hishamhm]

@Frityet I added a first-class self type to the language. We already had some heuristics before to detect methods based on the "self" name and type of the first argument. These heuristics have been adapted to detect the self type.

So, in current next, if you change your example above to say either one of:

local interface ISoundMaker
    makesound: function(self: ISoundMaker) -- heuristic: "self" name + definition type => "self" type
end

or

local interface ISoundMaker
    makesound: function(self: self) -- explicit
end

or

local interface ISoundMaker
    makesound: function(self) -- heuristic: "self" name on its own
end

then it will type-check.

[hishamhm]

Marking this as done! Thanks for reporting and for the test case, which I added to the test suite :)

[Frityet]

Marking this as done! Thanks for reporting and for the test case, which I added to the test suite :)

just tested, works like a charm