=== tests/cases/compiler/hidingIndexSignatures.ts ===
interface A {
>A : A, Symbol(A, Decl(hidingIndexSignatures.ts, 0, 0))

    [a: string]: {};
>a : string, Symbol(a, Decl(hidingIndexSignatures.ts, 1, 5))
}

interface B extends A {
>B : B, Symbol(B, Decl(hidingIndexSignatures.ts, 2, 1))
>A : A, Symbol(A, Decl(hidingIndexSignatures.ts, 0, 0))

    [a: string]: number; // Number is not a subtype of string.  Should error.
>a : string, Symbol(a, Decl(hidingIndexSignatures.ts, 5, 5))
}

var b: B;
>b : B, Symbol(b, Decl(hidingIndexSignatures.ts, 8, 3))
>B : B, Symbol(B, Decl(hidingIndexSignatures.ts, 2, 1))

b[""]; // Should be number
>b[""] : number
>b : B, Symbol(b, Decl(hidingIndexSignatures.ts, 8, 3))
>"" : string

var a: A;
>a : A, Symbol(a, Decl(hidingIndexSignatures.ts, 10, 3))
>A : A, Symbol(A, Decl(hidingIndexSignatures.ts, 0, 0))

a[""]; // Should be {}
>a[""] : {}
>a : A, Symbol(a, Decl(hidingIndexSignatures.ts, 10, 3))
>"" : string