Object spreading restrictions are inconsistent "Spread types may only be created from object types."

[vartan]

TypeScript Version: 3.3.3

function unsafeSpread<T extends number>(arg: T) {
  return {...arg}; // why isn't this an error
}
let val = 1;
let spreadVal = {...val}; // but this is
let unknownVal: unknown = 1;
let unknownSpreadVal = {...unknownVal}; // and this is not

Expected behavior:
"Spread types may only be created from object types." should be thrown whenever non-objects are spread.

Actual behavior:
unknown and generics can be spread regardless

Playground Link:
https://www.typescriptlang.org/play/#src=function%20unsafeSpread%3CT%20extends%20number%3E(arg%3A%20T)%20%7B%0D%0A%20%20return%20%7B...arg%7D%3B%20%2F%2F%20why%20isn't%20this%20an%20error%0D%0A%7D%0D%0Alet%20val%20%3D%201%3B%0D%0Alet%20spreadVal%20%3D%20%7B...val%7D%3B%20%2F%2F%20but%20this%20is%0D%0Alet%20unknownVal%3A%20unknown%20%3D%201%3B%0D%0Alet%20unknownSpreadVal%20%3D%20%7B...unknownVal%7D%3B%20%2F%2F%20and%20this%20is%20not%0D%0A

Related Issues:

did not find any in the first couple pages when searching

[jack-williams]

Also raised here. I suspect this might be a bug?

[collin5]

I've raised a PR that attempts to resolve the first scenario (spread on T) #31185. However, I'm still a little concerned about restricting spreading for any and unknown types as there is a possibility of this being a breaking change.

[orta]

I think it's fine to allow spreading on an any - unknown I think should fail. No need to add that in #31185 (but if you, dear reader, might be interested in raising your own PR for that - I'd help get that in )

[collin5]

Sure. I can have a PR for this by end of this weekend. Thank you.

[fatcerberus]

any in almost all contexts means "disable all type checking for this"; it would IMO be weird if it disabled spreading.