Array.prototype.sort make compareFn required in lib.d.ts

This is a suggestion to change the signature declaration of Array sort in lib.d.ts from

sort(compareFn?: (a: T, b: T) => number): this;

to

sort(this: string[], compareFn?: (a: string, b: string) => number): this;
sort(compareFn: (a: T, b: T) => number): this;

i.e. make compareFn non-optional for non-string arrays. This would result in errors in cases such as

[2, 10].sort() // returns [10, 2], i.e. sorted lexicographically, which is very unintuitive.

While this is strictly speaking a breaking change, it wouldn't be the first time the typings are stricter than the actually definitions.

lib.d.ts の Array.prototype.sort の宣言を読み、提案されたオーバーロードと比較してください。完了条件は、文字列以外の配列では compareFn が必須になり、文字列配列では引き続き compareFn が省略可能であることです；結果の型の挙動に照らして [2, 10].sort() の例を確認してください。