=== tests/cases/compiler/hidingIndexSignatures.ts ===
interface A {
>A : A

    [a: string]: {};
>a : string
}

interface B extends A {
>B : B
>A : A

    [a: string]: number; // Number is not a subtype of string.  Should error.
>a : string
}

var b: B;
>b : B
>B : B

b[""]; // Should be number
>b[""] : number
>b : B
>"" : string

var a: A;
>a : A
>A : A

a[""]; // Should be {}
>a[""] : {}
>a : A
>"" : string