Table interface definitions

[williamboman]

Hello! I'd like to be able to define a type alias to enforce table structures. Let me provide an example:

---@class Person
---@field name string
---@field greet fun(name: string): string

---@param person Person
local function speak(person)
    return person.greet(person.name)
end

speak { -- "Hello, John!"
  name = "John",
  speak = function(name)
    return string.format("Hello, %s!", name)
  end
}

-- I'd like this to produce a type error, as the provided table is invariant to Person.
speak {
  is_not = "a person"
}

-- I'd also like this to produce a type error.
---@type Person
local not_a_complete_person = { name = "Jane" }

In the above example I've used the @class annotation because it's easiest to express complex table structures by separating field definitions via @field, although @alias might be more appropriate.

Is it possible to achieve this level of type checking on table structures themselves, or should I use a different approach?

[firas-assaad]

I also would like a feature like that. As far as I know it's not possible, but I did suggest an idea for a similar feature: #1602

I was thinking more about inadvertently introducing additional fields, but the same kind of 'exact' types would also check that non-nil fields are always provided.