Type checker incorrectly refuses object spread of null or undefined

TypeScript Version: 2.2.0-dev.20161122

With --strictNullChecks.

Code

function spread(arg?: {}): {} {
  return {...arg}
}
spread()

Expected behavior:

spread() returns empty object {}.

Actual behavior:

Spread types may only be created from object types.

The spec specifically allows null and undefined spread arguments by having an early check before the ToObject abstract operation (3.1.2).

@Kovensky please give tonight's typescript@next a try and let us know if you are still seeing issues.

Mohamed Hegazy (@mhegazy)

Mohamed Hegazy (@mhegazy) is there a way to know which commit was used to build a given nightly?

The nightly snaps at 11:00 pm PST, anything merged in master before that should be there.

I found some cases where this is still an issue:

// Logs three empty objects without errors in JavaScript.
// Shows three "Spread types may only be created from object types." errors in TypeScript.
// Tested on TypeScript Playground on May 26, 2018.

const spread = <T extends object>(arg: T | null) => ({ ...arg })
console.log(spread(null), { ...null }, { ...undefined })

Playground link

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Type checker incorrectly refuses object spread of null or undefined #12460

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Type checker incorrectly refuses object spread of null or undefined #12460

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mhegazy commented on Nov 30, 2016

Jessidhia commented on Nov 30, 2016

mhegazy commented on Nov 30, 2016

mjomble commented on May 26, 2018

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