Ability to mark default constructor names for resolving return type

還沒有人認領這個 Issue。

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.



Start with the class.lua and example.lua scenarios in the issue, focusing on how the `---@class` annotation and `new()` call are resolved. Review the related discussion in issue #449 and the described `@field` alternative before choosing an approach. Done should include inferred constructor availability and the correct instance return type for the example.

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