Strict mode: Object is possibly 'null' when it really isn't

[zaggino]

TypeScript Version: 2.3.4

Code

/*
tsconfig.json
{
 "compilerOptions": {
 "target": "ES2015",
 "module": "commonjs",
 "strict": true
 }
}
*/

let maybeNumber = Math.random() > 0.5 ? 2 : null;
let ones = [1, 1, 1];
let twoes;
if (maybeNumber) {
 twoes = ones.map(x => x * maybeNumber);
}
console.log(maybeNumber, twoes);

Expected behavior:
Compilation passes, TS should know that .map function will be executed immediately and so maybeNumber will not be null

Actual behavior:
Compilation error: error TS2531: Object is possibly 'null'

Weird:
When I change let maybeNumber to const maybeNumber compilation passes for some reason, even though type of maybeNumber should be still number | null

[DanielRosenwasser]

See #9998.

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.