Ability to mark default constructor names for resolving return type

Hi!

A request to infer return value for default returns when calling a defined constructor function. EmmyLua supports this using a setting:

Here it can infer that calling e.g. :new() on items marked with the ---@class annotation will be returning an instance of that class.

This is especially useful when constructing classes using metatables in a generic class system, adding interfaces or inheritance functionality but still be able to denote the return type of calling the constructor method.

Example:

#class.lua

local definitions = {}

local Class = {}
function Class.class(name)
    local definitions = {}

    local def = definitions[name]
    if not def then
		def = {}
		def.__class_name = class_name

		def.new = function(self, ...)
	    	local instance = {}

	    	if instance.construct then
                instance:construct(...)
            end

            return instance
    	end

    	setmetatable(instance, def)

    	def[class_name] = def
	end

	return class_definition
end

Example of using the class creation method

#my_class.lua

local Class = require "path/class"

local MyClass = Class("MyClass")
function MyClass:construct()
	self._member = 0
end

Example of instantiating an instance of the class and showing the issue:

#example.lua

local MyClass = require "path/my_class"
local instance = MyClass:new() -- this line cannot find the function new() or deduce the return/type of "instance"

Here the instance of class return value from the new() function cannot be inferred and I haven't found a way to annotate this using luadocs with generics, alias, overload or other methods. This issue is somewhat related to #449 but I feel this warrants a retake on the proposed solution unless I am missing something?

A different way could be to allow explicit descriptors of the @field annotation to specify return value types in class definitions e.g.

The return values of functions defined in fields from a set metatable cannot have it's return type defined however it seems.

issue の class.lua と example.lua のシナリオから始め、---@class アノテーションと new() 呼び出しがどのように解決されるかに焦点を当ててください。アプローチを選択する前に、issue #449 の関連する議論と、説明されている @field の代替案を確認してください。完了時には、推論されたコンストラクターの利用可能性と、例における正しいインスタンスの戻り値型を含める必要があります。