unintended never type after a null check

[boopathi]

Bug Report

Some code flows like functions passed to array methods are not considered as immediately invoked and any assignment to a variable inside the array methods are not captured in the outer scope.

For example,

🔎 Search Terms

array methods, never, null check, assignment, variable assignment

🕗 Version & Regression Information

4.3.2

• This changed between versions 4.1.3 and 4.3.2

⏯ Playground Link

Playground link with relevant code

💻 Code

let map: Map<string, string> | null = null;

[1].map(() => { map = new Map() });

if (map != null) {
  // map is never
  console.log(map.get("something"));
}

🙁 Actual behavior

In the above code, after the null check, the variable map is expected to be of type Map<string,string>, but the assignment inside the Array.map function isn't captured and is considered as never.

Property 'get' does not exist on type 'never'.(2339)

🙂 Expected behavior

The variable map is of the type Map<string, string>

[whzx5byb]

Duplicate of #44025

[fatcerberus]

Root cause is #9998.

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.