When a rest parameter is referenced with a spread operator, the transformed code packs and unpacks it:

function foo(this: void, ...args: unknown[]) {
    console.log(...args);
}

=>

function foo(...)
    local args = ({...})
    print(unpack(args))
end

This PR adds a new directive @varArg to allow direct access to lua vararg operator .... This can be applied to an array-like type and any references to an identifier with that type will be directly transformed into ...:

/** @varArg */
interface LuaVarArg<T> extends Array<T> {}

function foo(this: void, ...args: LuaVarArg<unknown>) {
    console.log(...args);
}

=>

function foo(...)
    print(...)
end

Aside from function varargs, this can be used to access the file-scope varargs:

declare const arg: LuaVarArg<string>;
console.log(...arg);

=>

print(...)

To support tuple rest arguments, the vararg type must be declared like this:

/** @varArg */
type LuaVarArg<A extends unknown[]> = A & { __luaVarArg?: never };

function foo(this: void, ...args: LuaVarArg<[string, number]>) {
    console.log(...args);
}
foo("A", 2);

Note that this PR also adds stripping of the rest parameter variable (local args = ({...})) if it is not needed.