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

[catwell]

I tried reproducing this but could not.

Here are exactly the files I used:

-- a.tl

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

return A

-- b.tl

local type A <const> = require "a"

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

return B

local type A <const> = require "a"
local type B <const> = require "b"

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

I tried Teal master, 0.24.0 and 0.24.1 and I always get the correct generation.

[svermeulen]

Thanks for attempting to repro. I tried to narrow down repro steps more, and I realized that it actually does work, as long as I either run teal in the same directory as all these files, or a directory where it can find a tlconfig.lua file that includes the necessary directories such that it can locate all the files by require path.

You can repro the issue I had originally by running "tl gen [absolute path to main.tl]" from a directory that is not the one containing main.tl

So I assume this is working as intended. Maybe I should always run something like "tl check" before "tl gen" to ensure it doesn't generate invalid lua next time

[svermeulen]

I also found another way to fix this is to provide tl with the necessary include directories before running gen via the -I command line switch

[hishamhm]

I think we should change the behavior so that tl gen does tl gen --check by default (i.e. check and gen), and then introduce tl gen --no-check if someone wants to generate a file with type errors (which could be useful during the process of converting a codebase).

[hishamhm]

I'm closing this bug and opening #899, but I think I'm only going to merge that for Teal 0.25