Type information lost in named parameter list

[mhevery]

Given:

class A {
  constructor({name}: {name: string}) {}
}

Expecting:

class A {
  constructor({String name}) {}
}

But was:

class A {
  constructor({name}) {}
}

Notice missing String

//cc @vsmenon

[mhevery]

This blocks conversion of Angular 2 to DDC.