// @lib: es6 // https://github.com/Microsoft/TypeScript/issues/21962 export const SYM = Symbol('a unique symbol'); export interface I { [SYM]: 'sym'; [x: string]: 'str'; } let a: I = {[SYM]: 'sym'}; // Expect ok let b: I = {[SYM]: 'str'}; // Expect error