Declaring a var with interface type causes typescript to assume value can be undefined

[yuyaryshev]

TypeScript Version: 3.2.0-dev.201xxxxx
Done

Search Terms:
declare variable interface undefined

Code

interface ifc {
    a?:number[]
    b?:string
}

let x : ifc = {a:[1]};
//x.a = [1];        // no error if this line is uncommented
x.a.push(2);        // <<<<<<< TS2532: Object is possibly 'undefined'.
x.b = 'aaa';

Expected behavior:
No error with strictNullChecks

Actual behavior:
TS2532: Object is possibly 'undefined'.

Playground Link:
Enable strictNullChecks in options

http://www.typescriptlang.org/play/#src=interface%20ifc%20%7B%0D%0A%20%20%20%20a%3F%3Anumber%5B%5D%0D%0A%20%20%20%20b%3F%3Astring%0D%0A%7D%0D%0A%0D%0Alet%20x%20%3A%20ifc%20%3D%20%7Ba%3A%5B1%5D%7D%3B%0D%0A%2F%2Fx.a%20%3D%20%5B1%5D%3B%20%20%20%20%20%20%20%20%2F%2F%20no%20error%20if%20this%20line%20is%20uncommented%0D%0Ax.a.push(2)%3B%20%20%20%20%20%20%20%20%2F%2F%20%3C%3C%3C%3C%3C%3C%3C%20TS2532%3A%20Object%20is%20possibly%20'undefined'.%0D%0Ax.b%20%3D%20'aaa'%3B

[weswigham]

AFAIK this is because we don't include member initializers when considering control flow initializer narrowing.

[RyanCavanaugh]

Duplicate #20219

[typescript-bot]

This issue has been marked as a duplicate and has seen no activity in the last day. It has been closed for automatic house-keeping purposes.