tests/cases/conformance/types/tuple/optionalTupleElements1.ts(11,29): error TS1257: A required element cannot follow an optional element.
tests/cases/conformance/types/tuple/optionalTupleElements1.ts(15,5): error TS2322: Type 'T2' is not assignable to type 'T1'.
  Types of property '2' are incompatible.
    Type 'boolean | undefined' is not assignable to type 'boolean'.
      Type 'undefined' is not assignable to type 'boolean'.
tests/cases/conformance/types/tuple/optionalTupleElements1.ts(16,5): error TS2322: Type 'T3' is not assignable to type 'T1'.
  Types of property '1' are incompatible.
    Type 'string | undefined' is not assignable to type 'string'.
      Type 'undefined' is not assignable to type 'string'.
tests/cases/conformance/types/tuple/optionalTupleElements1.ts(17,5): error TS2322: Type 'T4' is not assignable to type 'T1'.
  Types of property '0' are incompatible.
    Type 'number | undefined' is not assignable to type 'number'.
      Type 'undefined' is not assignable to type 'number'.
tests/cases/conformance/types/tuple/optionalTupleElements1.ts(20,5): error TS2322: Type 'T3' is not assignable to type 'T2'.
  Types of property '1' are incompatible.
    Type 'string | undefined' is not assignable to type 'string'.
      Type 'undefined' is not assignable to type 'string'.
tests/cases/conformance/types/tuple/optionalTupleElements1.ts(21,5): error TS2322: Type 'T4' is not assignable to type 'T2'.
  Types of property '0' are incompatible.
    Type 'number | undefined' is not assignable to type 'number'.
      Type 'undefined' is not assignable to type 'number'.
tests/cases/conformance/types/tuple/optionalTupleElements1.ts(25,5): error TS2322: Type 'T4' is not assignable to type 'T3'.
  Types of property '0' are incompatible.
    Type 'number | undefined' is not assignable to type 'number'.
      Type 'undefined' is not assignable to type 'number'.


==== tests/cases/conformance/types/tuple/optionalTupleElements1.ts (7 errors) ====
    type T1 = [number, string, boolean];
    type T2 = [number, string, boolean?];
    type T3 = [number, string?, boolean?];
    type T4 = [number?, string?, boolean?];
    
    type L1 = T1["length"];
    type L2 = T2["length"];
    type L3 = T3["length"];
    type L4 = T4["length"];
    
    type T5 = [number, string?, boolean];  // Error
                                ~~~~~~~
!!! error TS1257: A required element cannot follow an optional element.
    
    function f1(t1: T1, t2: T2, t3: T3, t4: T4) {
        t1 = t1;
        t1 = t2;  // Error
        ~~
!!! error TS2322: Type 'T2' is not assignable to type 'T1'.
!!! error TS2322:   Types of property '2' are incompatible.
!!! error TS2322:     Type 'boolean | undefined' is not assignable to type 'boolean'.
!!! error TS2322:       Type 'undefined' is not assignable to type 'boolean'.
        t1 = t3;  // Error
        ~~
!!! error TS2322: Type 'T3' is not assignable to type 'T1'.
!!! error TS2322:   Types of property '1' are incompatible.
!!! error TS2322:     Type 'string | undefined' is not assignable to type 'string'.
!!! error TS2322:       Type 'undefined' is not assignable to type 'string'.
        t1 = t4;  // Error
        ~~
!!! error TS2322: Type 'T4' is not assignable to type 'T1'.
!!! error TS2322:   Types of property '0' are incompatible.
!!! error TS2322:     Type 'number | undefined' is not assignable to type 'number'.
!!! error TS2322:       Type 'undefined' is not assignable to type 'number'.
        t2 = t1;
        t2 = t2;
        t2 = t3;  // Error
        ~~
!!! error TS2322: Type 'T3' is not assignable to type 'T2'.
!!! error TS2322:   Types of property '1' are incompatible.
!!! error TS2322:     Type 'string | undefined' is not assignable to type 'string'.
!!! error TS2322:       Type 'undefined' is not assignable to type 'string'.
        t2 = t4;  // Error
        ~~
!!! error TS2322: Type 'T4' is not assignable to type 'T2'.
!!! error TS2322:   Types of property '0' are incompatible.
!!! error TS2322:     Type 'number | undefined' is not assignable to type 'number'.
!!! error TS2322:       Type 'undefined' is not assignable to type 'number'.
        t3 = t1;
        t3 = t2;
        t3 = t3;
        t3 = t4;  // Error
        ~~
!!! error TS2322: Type 'T4' is not assignable to type 'T3'.
!!! error TS2322:   Types of property '0' are incompatible.
!!! error TS2322:     Type 'number | undefined' is not assignable to type 'number'.
!!! error TS2322:       Type 'undefined' is not assignable to type 'number'.
        t4 = t1;
        t4 = t2;
        t4 = t3;
        t4 = t4;
    }
    
    let t2: T2;
    let t3: T3;
    let t4: T4;
    
    t2 = [42, "hello"];
    t3 = [42, "hello"];
    t3 = [42,,true]
    t3 = [42];
    t4 = [42, "hello"];
    t4 = [42,,true];
    t4 = [,"hello", true];
    t4 = [,,true];
    t4 = [];