indexSignatureWithTrailingComma.ts(2,17): error TS1025: An index signature cannot have a trailing comma.
indexSignatureWithTrailingComma.ts(6,17): error TS1025: An index signature cannot have a trailing comma.
indexSignatureWithTrailingComma.ts(10,17): error TS1025: An index signature cannot have a trailing comma.


==== indexSignatureWithTrailingComma.ts (3 errors) ====
    type A = {
        [key: string,]: string;
                    ~
!!! error TS1025: An index signature cannot have a trailing comma.
    };
    
    interface B {
        [key: string,]: string;
                    ~
!!! error TS1025: An index signature cannot have a trailing comma.
    }
    
    class C {
        [key: string,]: null;
                    ~
!!! error TS1025: An index signature cannot have a trailing comma.
    }
    