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