=== tests/cases/compiler/contextualSigInstantiationRestParams.ts ===
declare function toInstantiate<A, B>(a?: A, b?: B): B;
>toInstantiate : <A, B>(a?: A, b?: B) => B
>A : A
>B : B
>a : A
>A : A
>b : B
>B : B
>B : B

declare function contextual(...s: string[]): string
>contextual : (...s: string[]) => string
>s : string[]

var sig: typeof contextual = toInstantiate;
>sig : (...s: string[]) => string
>contextual : (...s: string[]) => string
>toInstantiate : <A, B>(a?: A, b?: B) => B