Support type promotion on this

[sigmundch]

Quite possibly this was already discussed, but I couldn't find the issue or discussion that cover this topic.

Today we have this behavior:

class A {
  foo() {
    if (this is B) {
      this.bar(); // ERROR
    }

    var x = this;
    if (x is B) {
       x.bar();  // OK
    }
  }
}
class B extends A {
  bar() {}
}
main() => new B().foo();

Should type promotion also be available on the implicit this variable (making the the first example behave like the second example with the local variable)?

[sigmundch]

Closing, I found now the issue tracking this: #1397