=== tests/cases/compiler/contextualSignatureInstatiationCovariance.ts ===
interface Animal { x }
>Animal : Animal
>x : any

interface TallThing { x2 }
>TallThing : TallThing
>x2 : any

interface Giraffe extends Animal, TallThing { y }
>Giraffe : Giraffe
>Animal : Animal
>TallThing : TallThing
>y : any

var f2: <T extends Giraffe>(x: T, y: T) => void;
>f2 : <T extends Giraffe>(x: T, y: T) => void
>T : T
>Giraffe : Giraffe
>x : T
>T : T
>y : T
>T : T

var g2: (a: Animal, t: TallThing) => void;
>g2 : (a: Animal, t: TallThing) => void
>a : Animal
>Animal : Animal
>t : TallThing
>TallThing : TallThing

g2 = f2; // While neither Animal nor TallThing satisfy the constraint, T is at worst a Giraffe and compatible with both via covariance.
>g2 = f2 : <T extends Giraffe>(x: T, y: T) => void
>g2 : (a: Animal, t: TallThing) => void
>f2 : <T extends Giraffe>(x: T, y: T) => void

var h2: (a1: Animal, a2: Animal) => void;
>h2 : (a1: Animal, a2: Animal) => void
>a1 : Animal
>Animal : Animal
>a2 : Animal
>Animal : Animal

h2 = f2; // Animal does not satisfy the constraint, but T is at worst a Giraffe and compatible with Animal via covariance.
>h2 = f2 : <T extends Giraffe>(x: T, y: T) => void
>h2 : (a1: Animal, a2: Animal) => void
>f2 : <T extends Giraffe>(x: T, y: T) => void