Type-unsafe usage of Record<string, () => void>

[paskozdilar]

🔎 Search Terms

TypeScript Record Function TypeError

🕗 Version & Regression Information

5.3.3

⏯ Playground Link

https://www.typescriptlang.org/play?#code/G4QwTgBAZgrgdgYwLYgA4C4ICUCmCD2YAJgDwDOALmAJZwDmANBABQCUEAvAHwTD7VEeHCAG8AvgG4AsAChQkWIk7R4yNAG0A5EXw4yEOPgoQcAD2qVNAXWkzFCNhIgB6ZxAAqAT1Q4AomDBCAEJZIA

💻 Code

var funcmap: Record<string, () => void> = {};
var func = funcmap['does not exist'];
func(); // TypeError!

🙁 Actual behavior

TypeScript compiles successfully (even with --strict option).
TypeScript infers the type of func variable to be () => void, even though it can be undefined when the key doesn't exist.

🙂 Expected behavior

TypeScript doesn't compile successfully, because the code didn't check whether func is undefined or not.

Additional information about the issue

No response

[jcalz]

Duplicates #13778 (see that and various linked issues there).

You're apparently looking for --noUncheckedIndexedAccess and for many people this turns out to be more annoying than helpful. Often the recommendation is to use (()=>void) | undefined instead of enabling this.

[paskozdilar]

Oh, I missed that one.
Thanks, I think that flag will do.
Cheers :)