When strictNullChecks is turned on:
(u: undefined, v: void, n: null) => {
v = u;
u = v; // type error: Type 'void' is not assignable to type 'undefined'
v = n; // type error: Type 'null' is not assignable to type 'void'
}
I'm curious about whether there exist values of type void that are not also of type undefined, especially with strictNullChecks enabled. Are there any instances where this statement holds true?
What values make this statement true?
The only method to receive a value of type void is by calling a function that returns void:
function f() { }
let x = f();
It's worth noting that it is possible to assign a non-void-returning function to a variable of type () => void, so the obtained void value may not necessarily be undefined, leading to the subtype relationship.
When it comes to assigning types to void, there are only two options: undefined and null. Void is exactly what its name suggests - the opposite of anything, the void, the absence of having a type.
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