Type identifying where clause behaviour changes when using interfaces loaded via require

[svermeulen]

local type A <const> = require("a")

-- local interface A
-- 	get_type: function(A): string
-- end

local type B <const> = require("b")

-- local interface B is A where self:get_type() == "b"
-- end

local b: A = {
	get_type = function(): string return "b" end
}

local c: A = {
	get_type = function(): string return "c" end
}

if c is B then
   print("is B")
else
   print("is not B")
end

The above code prints "is B" when it should print "is not B". If we stop using 'require' and place the contents of the files directly in the above code, then we correctly get "is not B". It seems that when included via files, the compiled lua code is this:

if type(c) == "table" then
   print("is B")
else
   print("is not B")
end

And when not using require it is this:

if c:get_type() == "b" then
   print("is B")
else
   print("is not B")
end