I'm struggling to understand the issue with this simple example
interface List {
"A": false,
"B": false,
}
// The function is missing a return statement and its return type does not include 'undefined'.ts(2366)
// I wonder why?
function bar<T extends keyof List>(letter: T): List[T] {
switch (letter) {
case "A":
return false
case "B":
return false
}
}
Which value would make letter result in an undefined return from my function?
If you're looking for a solution to your specific scenario, the following code snippet should work:
function bar(key: keyof Items): Items[typeof key] {
switch (key) {
case 'X':
return true;
case 'Y':
return false;
}
}
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