=== tests/cases/conformance/controlFlow/controlFlowInOperator.ts ===
const a = 'a';
>a : Symbol(a, Decl(controlFlowInOperator.ts, 0, 5))

const b = 'b';
>b : Symbol(b, Decl(controlFlowInOperator.ts, 1, 5))

const d = 'd';
>d : Symbol(d, Decl(controlFlowInOperator.ts, 2, 5))

type A = { [a]: number; };
>A : Symbol(A, Decl(controlFlowInOperator.ts, 2, 14))
>[a] : Symbol([a], Decl(controlFlowInOperator.ts, 4, 10))
>a : Symbol(a, Decl(controlFlowInOperator.ts, 0, 5))

type B = { [b]: string; };
>B : Symbol(B, Decl(controlFlowInOperator.ts, 4, 26))
>[b] : Symbol([b], Decl(controlFlowInOperator.ts, 5, 10))
>b : Symbol(b, Decl(controlFlowInOperator.ts, 1, 5))

declare const c: A | B;
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))
>A : Symbol(A, Decl(controlFlowInOperator.ts, 2, 14))
>B : Symbol(B, Decl(controlFlowInOperator.ts, 4, 26))

if ('a' in c) {
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))

    c;      // A
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))

    c['a']; // number;
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))
>'a' : Symbol([a], Decl(controlFlowInOperator.ts, 4, 10))
}

if ('d' in c) {
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))

    c; // never
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))
}

if (a in c) {
>a : Symbol(a, Decl(controlFlowInOperator.ts, 0, 5))
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))

    c;    // A
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))

    c[a]; // number;
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))
>a : Symbol(a, Decl(controlFlowInOperator.ts, 0, 5))
}

if (d in c) {
>d : Symbol(d, Decl(controlFlowInOperator.ts, 2, 5))
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))

    c; // never
>c : Symbol(c, Decl(controlFlowInOperator.ts, 7, 13))
}