Implement generalized iteration for looping over dictionaries and arrays with the index/key

[Daw588]

Luau on May 2022 received an update which implemented generalized iteration. Generalized iteration no longer requires developers to write pairs or ipairs. From my knowledge, roblox-ts has only one way to iterate through arrays and dictionaries with the index/key, which is the pairs() function, but it compiles to pairs which is no longer preferred.

Input:

const dictionary = {
	a: 1,
	b: 2,
	c: 3
};

for (const [i, v] of pairs(dictionary)) {
	print(i, v);
}

Output:

local dictionary = {
	a = 1,
	b = 2,
	c = 3,
}
for i, v in pairs(dictionary) do
	print(i, v)
end

I would want a way to make compiler output the code snippet below. However, I don't think it is a simple matter of just changing the output for pairs function, as a developer would expect it to generate the Luau pairs function. Perhaps we could make a macro function that acts like pairs but compiles to generalized iteration.

local dictionary = {
	a = 1,
	b = 2,
	c = 3,
}
for i, v in dictionary do
	print(i, v)
end

[zwinplayer64]

This doesn't make sense, pairs should compile to pairs and not generalized iteration

[Daw588]

I never stated in the post that pairs should compile to generalized iteration. I was asking for a way to iterate through dictionaries and arrays that would produce generalized iteration in the compiler output.

[Dionysusnu]

We've considered this before by giving objects a generic [Symbol.iterator] K,V definition. I'm not sure what the result of the discussion was back then, I can have a look later.