const x = {
    [1]: 2,
    [1]: 2,
//  ^^^ ERROR: An object literal cannot have multiple properties with the same name. (1117)
};

enum Enum { foo = 1, }

const y = {
    [Enum.foo]: 2,
    [Enum.foo]: 2,
//  ^^^^^^^^^^ No Error
};

    [Enum.foo]: 2,
    [Enum.foo]: 2,
//  ^^^^^^^^^^ An object literal cannot have multiple properties with the same name