how to use generics with arrow functions code example

Example 1: generic arrow function typescript

const foo = <T extends unknown>(x: T) => x;

Example 2: why can't define generic function in tsx file

const f = <T1, _>(arg1: T1) => {
   return { arg1 };
};

// or just adding a comma
const g = <T1,>(arg1: T1) => {
   return { arg1 };
};