interface A {
  kind: "A";
  a: number;
}

interface B {
  kind: "B";
  b: number;
}

declare const shouldBeB: (A | B) & B;
const b: B = shouldBeB; // works

function inGeneric<T extends A | B>(alsoShouldBeB: T & B) {
  const b: B = alsoShouldBeB;
  //    ~ TS2739: Type 'T & B' is missing the following properties from type 'B': kind, b
}