No compile error with Object.assign

[Strate]

interface Struct {
  a: boolean
  b: number
}
let v1: Struct = {a: true, b:1}
let v2: Struct = Object.assign({}, v1, {
  b: false
})

v2 variable now contains {a: true, b: false}, which is definetely not Struct type. But there is no compile-time error there. How come?

[ahejlsberg]

This is a duplicate of the issue raised in #6613. We currently don't have the ability to exactly express the exact semantics of Object.assign.