Map#has() should suffice for an undefined check when proceeding Map#get()

[SReject]

Suggestion

🔍 Search Terms

Map, map has

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

For instances cast as Map<>, a check of Map#has(key) should suffice as an undefined check for the key

📃 Motivating Example

Currently, we are required to have a redundant typecheck after a Map#has() for Map#get() calls:

const myMap : Map<string, string> = new Map();
myMap.set('key', 'value');

if (myMap.has('key')) {

  // ts(2322) - 'string | undefined' is not assignable to type 'string'
  const value : string = myMap.get('key');
}

This suggestion asks that ts infer the type as not a union with undefined if a Map#has() check has proceeded the Map#get() call

[MartinJohns]

Duplicate of #13086.

[SReject]

That is indeed the case. Closing