==== tests/cases/compiler/indexSignatureMustHaveTypeAnnotation.ts (4 errors) ====
    interface I {
        [x]: string;
         ~
!!! indexSignatureMustHaveTypeAnnotation.ts(2,6): error TS1022: Index signature parameter must have a type annotation.
        [x: string];
        ~~~~~~~~~~~
!!! indexSignatureMustHaveTypeAnnotation.ts(3,5): error TS1021: Index signature must have a type annotation.
    }
    
    class C {
        [x]: string
         ~
!!! indexSignatureMustHaveTypeAnnotation.ts(7,6): error TS1022: Index signature parameter must have a type annotation.
        
    }
    
    class C2 {
        [x: string]
        ~~~~~~~~~~~
!!! indexSignatureMustHaveTypeAnnotation.ts(12,5): error TS1021: Index signature must have a type annotation.
    }