TypeScript/tests/cases/compiler/indexSignatureMustHaveTypeAnnotation.ts

interface I {
    // Used to be indexer, now it is a computed property
    [x]: string;
    [x: string];
}

class C {
    // Used to be indexer, now it is a computed property
    [x]: string
    
}

class C2 {
    [x: string]
}