String#length と同じように、文字列リテラルの長さを計算します。
import type { Equal, Expect } from '@type-challenges/utils'
type cases = [
Expect<Equal<LengthOfString<''>, 0>>,
Expect<Equal<LengthOfString<'kumiko'>, 6>>,
Expect<Equal<LengthOfString<'reina'>, 5>>,
Expect<Equal<LengthOfString<'Sound! Euphonium'>, 16>>,
]