Void parameter still required when type extends generic

TypeScript Version: 3.2.2

Search Terms:
void parameter type extends generic
Code

function works1(n: number, b: void) { }

works1(12);

function works2(n: number, b: 1 extends 1 ? void : number) { }

works2(12);

function fails<T>(n: number, b: T extends 1 ? void : number) { }

fails<2>(12, 2);  // works, requires both params
fails<1>(12);  // fails, requires 2 parameters even though second param is void

Expected behavior:
That I can ignore the second parameter since its void

Actual behavior:
Ts tells me I am missing a parameter

https://www.typescriptlang.org/play/index.html#src=function%20works1(n%3A%20number%2C%20b%3A%20void)%20%7B%20%7D%0D%0A%0D%0Aworks1(12)%3B%0D%0A%0D%0Afunction%20works2(n%3A%20number%2C%20b%3A%201%20extends%201%3F%20void%20%3A%20number)%20%7B%20%7D%0D%0A%0D%0Aworks2(12)%3B%0D%0A%0D%0Afunction%20fails%3CT%3E(n%3A%20number%2C%20b%3A%20T%20extends%201%3Fvoid%3Anumber)%20%7B%20%7D%0D%0A%0D%0Afails%3C2%3E(12%2C2)%3B%20%20%2F%2Fworks%2C%20requires%20both%20params%0D%0Afails%3C1%3E(12)%3B%20%20%2F%2F%20requires%202%20parameters%20even%20though%20second%20param%20is%20void%0D%0A

Start by running the minimal generic conditional-type example from the issue with TypeScript 3.2.2 and compare it with the non-generic cases. Trace how the compiler determines whether the second parameter is required for fails<1> and fails<2>; done means the generic void case accepts the omitted argument while the number case still requires it.