interface object couldn't extends Record

Question

why interface couldn't extend Record

interface Data {
  a: string
}

Data extends Record ? 'yes' : 'no' // 'no'

however, if I change the Data to type it works fine

type Data {
  a: string
}
 
Data extends Record ? 'yes' : 'no' // 'yes'

user_11811623 · Answer

type T = Record evaluates to { [x: string]: unknown; }

Object types have an implicit index signature, but interfaces don't (for safety reasons), so they don't extend an index type.

interface object couldn't extends Record<string, unknown>