Pick non-null member of nullable mapped type

[NN---]

I have a simple code which checks property for null and throws exception if it is null or returns the value.

function getNonNull<T extends object, K extends keyof T>(obj: T, key: K): T[K] {
 const v = obj[key]; 
 if (v != null) {
 return v;
 } else {
 throw "A";
 }
} 

The only catch that it doesn't say it returns non-null value.

const a = getNonNull({a:null},"a"); // a : null

I am trying to improve function to set 'obj' as an object of type [K in string]: U | null | undefined and then TypeScript would return 'U'.

Unfortunately TypeScript doesn't like it and types 'U' as '{}' instead of correct type.

function getNonNull<
 U,
 T extends {[K in string]: U | null | undefined },
 K extends keyof T
 >(obj: T, key: K): T[K] {
 
 const v = obj[key]; 
 if (v != null) {
// error TS2322: Type 'T[K]' is not assignable to type 'U'.
// Type 'U | null | undefined' is not assignable to type 'U'.
// Type 'undefined' is not assignable to type 'U'.
 return v; 
 } else {
 throw "A";
 }
} 

Do I miss something ?

[mhegazy]

looks like the same issue as #14366.

[mhegazy]

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