file1.ts(35,1): error TS2454: Variable 'c5' is used before being assigned.
file1.ts(36,1): error TS2454: Variable 'c5' is used before being assigned.
file1.ts(37,1): error TS2454: Variable 'c5' is used before being assigned.
file1.ts(38,1): error TS2454: Variable 'c5' is used before being assigned.


==== file1.ts (4 errors) ====
    declare class C1 { }
    
    interface C1 { }
    
    interface C2 { }
    
    declare class C2 { }
    
    class C3 { }
    
    interface C3 { }
    
    interface C4 { }
    
    class C4 { }
    
    interface C5 {
        x1: number;
    }
    
    declare class C5 {
        x2: number;
    }
    
    interface C5 {
        x3: number;
    }
    
    interface C5 {
        x4: number;
    }
    
    // checks if properties actually were merged
    var c5 : C5;
    c5.x1;
    ~~
!!! error TS2454: Variable 'c5' is used before being assigned.
    c5.x2;
    ~~
!!! error TS2454: Variable 'c5' is used before being assigned.
    c5.x3;
    ~~
!!! error TS2454: Variable 'c5' is used before being assigned.
    c5.x4;
    ~~
!!! error TS2454: Variable 'c5' is used before being assigned.
    
==== file2.ts (0 errors) ====
    declare class C6 { }
    
    interface C7 { }
    
==== file3.ts (0 errors) ====
    interface C6 { }
    
    declare class C7 { }