Add empty variable declaration support

[b1ek]

okay so i've implemented empty variable declarations for this syntax:

let variable: Text
let variable // wont work: generic not allowed

it translates like this: let variable: Text -> declare variable

and if the variable was declared but never assigned, it will throw a compile time error

closes #420

[KrosFire]

Why do we use Arc here?

[KrosFire]

Why cant we allow for this syntax?

let x: Text = fun_returning_any()

[b1ek]

we can, its just not relevant in this PR. you should create another issue for that

[b1ek]

Why do we use Arc here?

Mutex<T> can't be cloned, so Arc must be used so it can be cloned but pointing to the same location as the first Arc

[mks-h]

This logic doesn't track different execution branches. Here's an examle:

fun test(arg: Num): Null {
        let var: Text
        if {
                arg < 20: var = "Hello, World!"
                arg > 30: var = "Hi, hello!"
        }
        echo var
}

test(10) // outputs "Hello, World!"
test(25) // outputs empty message, shouldn't be possible
test(40) // outputs "Hi, hello!"

Variable is being assigned only in two branches, but is always used. This means it also gets used when uninitialized.

[b1ek]

so we can't actually track if its assigned in a way that would matter. i think we should remove that check for now and implement it later when we start actually analyzing code for errors. @Ph0enixKM @Mte90 what do you think

[Mte90]

It make sense what @b1ek, probably what we can do is adding a comment right in the code with \\TODO so we can found it when we want to do that.
I think that we already have a ticket for errors alerting?

[mks-h]

I say we shouldn't implement this language feature until we can make it work as intended. There are enough workarounds for it, so this shouldn't be a problem.

[mks-h]

we can offer the feature right now

*offer a broken feature

it is normal that we optimize it's output.

This isn't about output optimization, this is about correctness and soundness of the language. Optimization is when something already works, but is made to work better. This doesn't work.

[Mte90]

Sorry I confused the PR with another one about constants...

About my proposal is to do what is written here #432 (comment)

[KrosFire]

Why do we use Arc here?

Mutex<T> can't be cloned, so Arc must be used so it can be cloned but pointing to the same location as the first Arc

I get that, but we don't use Mutex anywhere else in this project as we don't utilize multi threading. Why do we need it now?

[Ph0enixKM]

I agree with @mks-h. The features implemented should work as expected from the ground up. Otherwise people will start to use it in an unintended way. Thus when we introduce a fix for this issue, then it will create a breaking change.

[b1ek]

im converting this to draft before we implement a proper solution for code scanning