Support decorators on function declarations

[SergioMorchon]

Hi all.

I think it would be a great feature if we can use decorators with functions too.

Example

// SImple use case
function deprecated(target: Function) {
    let oldFunction = target;
    return (...args) {
        console.log("You are using a deprecated function").
        return oldFunction.apply(null, args);
    };
}

@deprecated
function legacy(...args) {/* ... */};

It also would enable patterns like Contract, with pre/post conditions checks etc.

[DanielRosenwasser]

Hi @SergioMorchon, thanks for the suggestion. Functions are hoisted, so what are the intended semantics? See the conversation at #2249 (comment).

That's the main problem, and the ECMA-262 committee doesn't seem totally sure what to do about it either. We'd need more details, so this is a suggestion at this point, not a proposal. See our guide on writing good design proposals.

[mhegazy]

Any thing that typescript will support in this domain needs to be inline with the ES proposal. see wycats/javascript-decorators#31 for related discussion.

[mhegazy]

The JS-decorator proposal is the right place to have this discussion. Please submit the proposal on https://github.com/wycats/javascript-decorators repo instead.

[SergioMorchon]

@mhegazy definitely agree, thank you for the info!