casting? and "attempt to call value of type '((void) -> (any*) | nil)'"

[daurnimator]

Trying to run:

interface foo
    unpack: (self) -> (number)
end
local t:foo = load("return {n=1; unpack = function(self) return self.n end}", nil, nil, nil)();
print(t:unpack())

Gives errors:

/dev/stdin:1:61: type error, attempt to call value of type '((void) -> (any*) | nil)'
/dev/stdin:1:53: type error, attempt to assign 'nil' to '{unpack:(self) -> (number)}'
/dev/stdin:1:149: type error, attempt to pass '(void)' to field of input type '(self)'

FWIW, I got this while trying to reproduce a different error as a test case.

[kevinclancy]

I think part of the problem is that the value load returns might be nil. If that's the case, then you can't call it. You probably need to check that its type or value is not nil before calling it, but I'm not sure how that is done in typed lua.

The example here might be relevant:
https://github.com/andremm/typedlua/blob/master/examples/typical/typical.tl

You should be able to do this:
local ret = load("return {n=1; unpack = function(self) return self.n end}", nil, nil, nil)
if ret then
local t:foo = ret()
print(t:unpack())
end

Does that work?

[andremm]

Thanks for the reply Kevin. It is perfect.

[daurnimator]

okay thanks. turns out this wasn't how to replicate my original issue.

Not sure if I should open a new issue, I'll try and ask here.
I was looking into providing type annotations for luatz.

As luatz/timetable.tld:

interface timetable
        year: number
        month: number
        day: number
        hour: number
        min: number
        sec: number
        yday: number
        wday: number

        unpack: (self) -> (number, number, number, number, number, number)
        normalise: (self) -> (self)
        timestamp: (self) -> (number)
        rfc_3339: (self) -> (string)
        strftime: (self, string) -> (string)
end

new: (number, number, number, number, number, number) -> (timetable)
new_from_timestamp: (number) -> (timetable)
cast: (any) -> (timetable)

local t:timetable = require"luatz.timetable".new_from_timestamp(123);
print(t:unpack())

I get the error:

/dev/stdin:1:77: type error, attempt to pass '(void)' to field of input type '(self)'

[andremm]

I just pushed a commit that should fix this problem. Can you please pull it and test if it works?

[daurnimator]

Looks like that fixed it!

[andremm]

Cool! Thanks for the report.

[daurnimator]

btw; is that the correct way to define a 'class'? the first items listed are actual contents; the later items are methods attached via __index.

And complete off topic now: do .tld files have a way to require/import other definitions?

[andremm]

No, there is still not way to require/import other definitions inside .tld files.

Chapter 3 of my WIP PhD thesis includes a section about Object-Oriented programming with Typed Lua.
Did you check that?

[daurnimator]

Thanks!

[daurnimator]

No, there is still not way to require/import other definitions inside .tld files.

Is this still the case? Want me to open a new issue?

[andremm]

Is this still the case? Want me to open a new issue?

Yes, this is still the case and please open an issue for this. Thanks!