Why do some comments disappear in compiled TypeScript output while others remain?

Here's my TypeScript code:

// Enum
enum Direction {
    North = 1,
    East,
    West,
    South
}

console.log(Direction.East);

// Literal types
function yesOrNoQuestion(ans: "yes" | "no"): void {
    console.log("You said", ans);
}

yesOrNoQuestion("yes");

// Tuple
type rgb = [red: number, green: number, blue: number];
const color: rgb = [10, 255, 255];
console.log(color);

const tuple: [boolean, string] = [true, "yes"];
console.log(tuple);

Here's the compiled code:

"use strict";
// Enum
var Direction;
(function (Direction) {
    Direction[Direction["North"] = 1] = "North";
    Direction[Direction["East"] = 2] = "East";
    Direction[Direction["West"] = 3] = "West";
    Direction[Direction["South"] = 4] = "South";
})(Direction || (Direction = {}));
console.log(Direction.East);
// Literal types
function yesOrNoQuestion(ans) {
    console.log("You said", ans);
}
yesOrNoQuestion("yes");
const color = [10, 255, 255];
console.log(color);
const tuple = [true, "yes"];
console.log(tuple);

I have 3 comments in my TS code (Enum, Literal types, Tuple). But, the compiled code has only the first two comments. Is there any reason for that? TS should either keep all comments or remove all comments. Why is it only removing specific comments?

I didn't explicitly set "removeComments" in my tsconfig.json:

{
    "compilerOptions": {
        "target": "ES6",
        "strict": true,
        "strictNullChecks": true,
        "strictFunctionTypes": true,
        "alwaysStrict": true
    }
}

I compiled using npx tsc command.

I expected either:

• All three comments to be preserved, or
• All three comments to be removed

But TypeScript only preserved the first two. I didn’t set "removeComments" explicitly.

So, I am wondering:

• Is there any rule or logic TypeScript uses to keep/remove certain comments?
• Is this due to optimization or code transformation?
• Or is this just a config issue?

In TS comments are always attached to some piece of code

In your case // Tuple is attached to a compile time only code, a type definition.

This is why you don't see it in the output.