Object rest destructuring parameter defaults to empty object, causing errors when untyped

[billti]

Using the latest release-2.1 branch, I'm seeing the following behavior.

I'm writing some React/JSX code, and using a pattern often seen in code in the wild, namely:

var fails = ({myId, ...others}) => <div id={myId}>{others.anything}</div>;

However, the above is in error, as the type inferred for ...others is the empty object ({}). Thus the expression within the DIV tags gives the error Property 'anything' does not exist on type '{}'.

If I explicitly type the parameter then all is OK. Namely:

interface Sample {
    myId: string;
    anything: number;
}

var works = ({myId, ...others}: Sample) => <div id={myId}>{others.anything}</div>;

It seems to me that for the ease of writing (and porting existing code), ...others above should default to any, as other untyped parameters do.

This may have already been discussed in some of the other rest/spread discussions. I did trying to find a definitive explanation, but those threads were quite verbose. Apologies if already covered.

Ping @sandersn , @RyanCavanaugh , @mhegazy

[sandersn]

That's an oversight I think. The machinery that infers a contextual type for binding patterns needs to be updated for object rest so that it propagates the any through to `others`.

…

_____________________________ From: Bill Ticehurst <notifications@github.com<mailto:notifications@github.com>> Sent: Saturday, November 26, 2016 9:45 PM Subject: [Microsoft/TypeScript] Object rest destructuring parameter defaults to empty object, causing errors when untyped (#12519) To: Microsoft/TypeScript <typescript@noreply.github.com<mailto:typescript@noreply.github.com>> Cc: Nathan Shively-Sanders <nathansa@microsoft.com<mailto:nathansa@microsoft.com>>, Mention <mention@noreply.github.com<mailto:mention@noreply.github.com>> Using the latest release-2.1 branch, I'm seeing the following behavior. I'm writing some React/JSX code, and using a pattern often seen in code in the wild, namely: var fails = ({myId, ...others}) => <div id={myId}>{others.anything}</div>; However, the above is in error, as the type inferred for ...others is the empty object ({}). Thus the expression within the DIV tags gives the errorProperty 'anything' does not exist on type '{}'. If I explicitly type the parameter then all is OK. Namely: interface Sample { myId: string; anything: number;}var works = ({myId, ...others}: Sample) => <div id={myId}>{others.anything}</div>; It seems to me that for the ease or writing/porting existing code, ...others above should default toany, as other untyped parameters do. This may have already been discussed in some of the other rest/spread discussions. I did trying to find a definitive explanation, but those threads were quite verbose. Apologies if already covered. Ping @sandersn<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitpro.ttaallkk.top%2Fsandersn&data=02%7C01%7Cnathansa%40microsoft.com%7C0c434fd9fedc46cd956e08d416888991%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636158223065835432&sdata=vgtxz5J34e0U%2B8xJjrBvFJZ9FEORsQEt7ul71Bh1N2s%3D&reserved=0> , @RyanCavanaugh<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitpro.ttaallkk.top%2FRyanCavanaugh&data=02%7C01%7Cnathansa%40microsoft.com%7C0c434fd9fedc46cd956e08d416888991%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636158223065845440&sdata=1WtqsR%2BuD78%2BTdfmNELb1t%2FMtZBtv1sY2%2BRd%2B7itOb0%3D&reserved=0> , @mhegazy<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitpro.ttaallkk.top%2Fmhegazy&data=02%7C01%7Cnathansa%40microsoft.com%7C0c434fd9fedc46cd956e08d416888991%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636158223065845440&sdata=gk9Q5xmyZ8%2B%2FwNA%2BVeuq1toxQCDH7kgTRYDejl8aJpk%3D&reserved=0> - You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitpro.ttaallkk.top%2FMicrosoft%2FTypeScript%2Fissues%2F12519&data=02%7C01%7Cnathansa%40microsoft.com%7C0c434fd9fedc46cd956e08d416888991%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636158223065845440&sdata=iLUikvHOQk7A54B64mWn1iKYmm49VA403wqNWxp1z7A%3D&reserved=0>, or mute the thread<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitpro.ttaallkk.top%2Fnotifications%2Funsubscribe-auth%2FAAR6YeV-m98bhKvRYDadCtidgUHUdqqsks5rCRjfgaJpZM4K9EhO&data=02%7C01%7Cnathansa%40microsoft.com%7C0c434fd9fedc46cd956e08d416888991%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636158223065845440&sdata=xlXPaS%2FvTUsCrcpgRvo4UYPLQFxfyulwn5IiWJvXUY8%3D&reserved=0>.