callSignatureAssignabilityInInheritance4.ts(3,14): error TS2564: Property 'foo' has no initializer and is not definitely assigned in the constructor.
callSignatureAssignabilityInInheritance4.ts(4,30): error TS2564: Property 'bar' has no initializer and is not definitely assigned in the constructor.
callSignatureAssignabilityInInheritance4.ts(5,34): error TS2564: Property 'baz' has no initializer and is not definitely assigned in the constructor.
callSignatureAssignabilityInInheritance4.ts(6,35): error TS2564: Property 'bing' has no initializer and is not definitely assigned in the constructor.


==== callSignatureAssignabilityInInheritance4.ts (4 errors) ====
    // checking subtype relations for function types as it relates to contextual signature instantiation
    
    class Base { foo: string; }
                 ~~~
!!! error TS2564: Property 'foo' has no initializer and is not definitely assigned in the constructor.
    class Derived extends Base { bar: string; }
                                 ~~~
!!! error TS2564: Property 'bar' has no initializer and is not definitely assigned in the constructor.
    class Derived2 extends Derived { baz: string; }
                                     ~~~
!!! error TS2564: Property 'baz' has no initializer and is not definitely assigned in the constructor.
    class OtherDerived extends Base { bing: string; }
                                      ~~~~
!!! error TS2564: Property 'bing' has no initializer and is not definitely assigned in the constructor.
    
    interface A { // T
        // M's
        a: <T>(x: T) => T[];
        a2: <T>(x: T) => string[];
        a3: <T>(x: T) => void;
        a4: <T,U>(x: T, y: U) => string;
        a5: <T,U>(x: (arg: T) => U) => T;
        a6: <T extends Base>(x: (arg: T) => Derived) => T;
        a11: <T>(x: { foo: T }, y: { foo: T; bar: T }) => Base;
        a15: <T>(x: { a: T; b: T }) => T[];
        a16: <T extends Base>(x: { a: T; b: T }) => T[];
        a17: {
            <T extends Derived>(x: (a: T) => T): T[];
            <T extends Base>(x: (a: T) => T): T[];        
        };
        a18: {
            (x: {
                <T extends Derived>(a: T): T;
                <T extends Base>(a: T): T;
            }): any[];
            (x: {
                <T extends Derived2>(a: T): T;
                <T extends Base>(a: T): T;
            }): any[];
        };
    }
    
    // S's
    interface I extends A {
        // N's
        a: <T>(x: T) => T[]; // ok, instantiation of N is a subtype of M, T is number
        a2: <T>(x: T) => string[]; // ok
        a3: <T>(x: T) => T; // ok since Base returns void
        a4: <T, U>(x: T, y: U) => string; // ok, instantiation of N is a subtype of M, T is string, U is number
        a5: <T, U>(x: (arg: T) => U) => T; // ok, U is in a parameter position so inferences can be made
        a6: <T extends Base, U extends Derived>(x: (arg: T) => U) => T; // ok, same as a5 but with object type hierarchy
        a11: <T, U>(x: { foo: T }, y: { foo: U; bar: U }) => Base; // ok
        a15: <U, V>(x: { a: U; b: V; }) => U[]; // ok, T = U, T = V
        a16: <T>(x: { a: T; b: T }) => T[]; // ok, more general parameter type
        a17: <T>(x: (a: T) => T) => T[]; // ok
        a18: (x: <T>(a: T) => T) => any[]; // ok
    }