stringIndexerAssignments2.ts(19,1): error TS2322: Type 'C2' is not assignable to type 'C1'.
  Index signature for type 'string' is missing in type 'C2'.
stringIndexerAssignments2.ts(20,1): error TS2322: Type 'C3' is not assignable to type 'C1'.
  Types of property 'one' are incompatible.
    Type 'number' is not assignable to type 'string'.


==== stringIndexerAssignments2.ts (2 errors) ====
    class C1 {
        [index: string]: string
        one!: string;
    }
    
    class C2 {
        one!: string;
    }
    
    class C3 {
        one!: number;
        two!: string;
    }
    
    declare var x: C1;
    declare var a: C2;
    declare var b: C3;
    
    x = a;
    ~
!!! error TS2322: Type 'C2' is not assignable to type 'C1'.
!!! error TS2322:   Index signature for type 'string' is missing in type 'C2'.
    x = b;
    ~
!!! error TS2322: Type 'C3' is not assignable to type 'C1'.
!!! error TS2322:   Types of property 'one' are incompatible.
!!! error TS2322:     Type 'number' is not assignable to type 'string'.