co19/LanguageFeatures/Extension-types/promotion_A01_t01

[scheglov]

  ET2<num?> et2 = ET2(2);
  if (et2.id != null) {
    et2.id.isEven;
  }

Do we expect promotion of et2 to ET2<int> in the declaration?
I think this does not happen, by two reasons:

1. ET2(2) is inferred as ET2<num?>, not ET2<int>.
2. The declaration of et2 does not promote it to ET2<int> anyway, because it is not a type of interest.

[eernstg]

(This test will be updated one more time, because promotion of a representation variable isn't sound in the first place.)

Edit: That wasn't true, cf. dart-lang/sdk#53446, promotion of a representation variable is sound. However, it's still not determined exactly when the promotion is allowed to take place.

If et2.id is allowed to be promoted in the example then isEven should still be a compile-time error, but et2.id should be promoted from num? to num, and it should then be allowed to invoke a method like floor().

[eernstg]

I can see that the test has now been updated to promote et2.id to int. That should work if promotion of et2.id is allowed in the first place.

Awaiting the discussion in dart-lang/sdk#53446 for that.

[sgrekhov]

Resolved by #2279