nominal typing in class

[xiaoxiangmoe]

TypeScript Version: 3.3.0-dev.201xxxxx

Search Terms:

class, nominal typing, structural typing
Code

interface A {
  color:string
}

interface B {
  color:string
}

const b:B = {
  color:'red'
}



function foo(a:A){
  return String(a)
}

foo(b)


class AA{
  constructor(color:string){
    this.color=color
  }
  color:string
}
class BB{
  constructor(color:string){
    this.color=color
  }
  color:string
}

const bb = new BB('red')


function bar(a:AA){
  return String(a)
}

bar(bb)

Expected behavior:

class should be nominal typing,
show error in bar(bb)

Actual behavior:

class be structural typing,
no error

Playground Link:

structural typing & nominal typing

[j-oliveras]

Duplicate/related to #202, #12936 and PR #28749.

[DanielRosenwasser]

P.S. @j-oliveras I really appreciate you helping out with these issues