subtypingWithCallSignatures2.types

//// [tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithCallSignatures2.ts] ////

=== subtypingWithCallSignatures2.ts ===
// checking subtype relations for function types as it relates to contextual signature instantiation

class Base { foo: string; }
>Base : Base
>     : ^^^^
>foo : string
>    : ^^^^^^

class Derived extends Base { bar: string; }
>Derived : Derived
>        : ^^^^^^^
>Base : Base
>     : ^^^^
>bar : string
>    : ^^^^^^

class Derived2 extends Derived { baz: string; }
>Derived2 : Derived2
>         : ^^^^^^^^
>Derived : Derived
>        : ^^^^^^^
>baz : string
>    : ^^^^^^

class OtherDerived extends Base { bing: string; }
>OtherDerived : OtherDerived
>             : ^^^^^^^^^^^^
>Base : Base
>     : ^^^^
>bing : string
>     : ^^^^^^

declare function foo1(a: (x: number) => number[]): typeof a;
>foo1 : { (a: (x: number) => number[]): typeof a; (a: any): any; }
>     : ^^^ ^^                       ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: number) => number[]
>  : ^ ^^      ^^^^^        
>x : number
>  : ^^^^^^
>a : (x: number) => number[]
>  : ^ ^^      ^^^^^^^^^^^^^

declare function foo1(a: any): any;
>foo1 : { (a: (x: number) => number[]): (x: number) => number[]; (a: any): any; }
>     : ^^^ ^^                       ^^^^ ^^      ^^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo2(a: (x: number) => string[]): typeof a;
>foo2 : { (a: (x: number) => string[]): typeof a; (a: any): any; }
>     : ^^^ ^^                       ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: number) => string[]
>  : ^ ^^      ^^^^^        
>x : number
>  : ^^^^^^
>a : (x: number) => string[]
>  : ^ ^^      ^^^^^^^^^^^^^

declare function foo2(a: any): any;
>foo2 : { (a: (x: number) => string[]): (x: number) => string[]; (a: any): any; }
>     : ^^^ ^^                       ^^^^ ^^      ^^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo3(a: (x: number) => void): typeof a;
>foo3 : { (a: (x: number) => void): typeof a; (a: any): any; }
>     : ^^^ ^^                   ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: number) => void
>  : ^ ^^      ^^^^^    
>x : number
>  : ^^^^^^
>a : (x: number) => void
>  : ^ ^^      ^^^^^^^^^

declare function foo3(a: any): any;
>foo3 : { (a: (x: number) => void): (x: number) => void; (a: any): any; }
>     : ^^^ ^^                   ^^^^ ^^      ^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo4(a: (x: string, y: number) => string): typeof a;
>foo4 : { (a: (x: string, y: number) => string): typeof a; (a: any): any; }
>     : ^^^ ^^                                ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: string, y: number) => string
>  : ^ ^^      ^^ ^^      ^^^^^      
>x : string
>  : ^^^^^^
>y : number
>  : ^^^^^^
>a : (x: string, y: number) => string
>  : ^ ^^      ^^ ^^      ^^^^^^^^^^^

declare function foo4(a: any): any;
>foo4 : { (a: (x: string, y: number) => string): (x: string, y: number) => string; (a: any): any; }
>     : ^^^ ^^                                ^^^^ ^^      ^^ ^^      ^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo5(a: (x: (arg: string) => number) => string): typeof a;
>foo5 : { (a: (x: (arg: string) => number) => string): typeof a; (a: any): any; }
>     : ^^^ ^^                                      ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: (arg: string) => number) => string
>  : ^ ^^                       ^^^^^      
>x : (arg: string) => number
>  : ^   ^^      ^^^^^      
>arg : string
>    : ^^^^^^
>a : (x: (arg: string) => number) => string
>  : ^ ^^                       ^^^^^^^^^^^

declare function foo5(a: any): any;
>foo5 : { (a: (x: (arg: string) => number) => string): (x: (arg: string) => number) => string; (a: any): any; }
>     : ^^^ ^^                                      ^^^^ ^^                       ^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo6(a: (x: (arg: Base) => Derived) => Base): typeof a;
>foo6 : { (a: (x: (arg: Base) => Derived) => Base): typeof a; (a: any): any; }
>     : ^^^ ^^                                   ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: (arg: Base) => Derived) => Base
>  : ^ ^^                      ^^^^^    
>x : (arg: Base) => Derived
>  : ^   ^^    ^^^^^       
>arg : Base
>    : ^^^^
>a : (x: (arg: Base) => Derived) => Base
>  : ^ ^^                      ^^^^^^^^^

declare function foo6(a: any): any;
>foo6 : { (a: (x: (arg: Base) => Derived) => Base): (x: (arg: Base) => Derived) => Base; (a: any): any; }
>     : ^^^ ^^                                   ^^^^ ^^                      ^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo7(a: (x: (arg: Base) => Derived) => (r: Base) => Derived): typeof a;
>foo7 : { (a: (x: (arg: Base) => Derived) => (r: Base) => Derived): typeof a; (a: any): any; }
>     : ^^^ ^^                                                   ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: (arg: Base) => Derived) => (r: Base) => Derived
>  : ^ ^^                      ^^^^^                    
>x : (arg: Base) => Derived
>  : ^   ^^    ^^^^^       
>arg : Base
>    : ^^^^
>r : Base
>  : ^^^^
>a : (x: (arg: Base) => Derived) => (r: Base) => Derived
>  : ^ ^^                      ^^^^^^ ^^    ^^^^^^^^^^^^

declare function foo7(a: any): any;
>foo7 : { (a: (x: (arg: Base) => Derived) => (r: Base) => Derived): (x: (arg: Base) => Derived) => (r: Base) => Derived; (a: any): any; }
>     : ^^^ ^^                                                   ^^^^ ^^                      ^^^^^^ ^^    ^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo8(a: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived): typeof a;
>foo8 : { (a: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived): typeof a; (a: any): any; }
>     : ^^^ ^^                                                                               ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>  : ^ ^^                      ^^ ^^                       ^^^^^                    
>x : (arg: Base) => Derived
>  : ^   ^^    ^^^^^       
>arg : Base
>    : ^^^^
>y : (arg2: Base) => Derived
>  : ^    ^^    ^^^^^       
>arg2 : Base
>     : ^^^^
>r : Base
>  : ^^^^
>a : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>  : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^

declare function foo8(a: any): any;
>foo8 : { (a: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived): (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived; (a: any): any; }
>     : ^^^ ^^                                                                               ^^^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo9(a: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived): typeof a;
>foo9 : { (a: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived): typeof a; (a: any): any; }
>     : ^^^ ^^                                                                               ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>  : ^ ^^                      ^^ ^^                       ^^^^^                    
>x : (arg: Base) => Derived
>  : ^   ^^    ^^^^^       
>arg : Base
>    : ^^^^
>y : (arg2: Base) => Derived
>  : ^    ^^    ^^^^^       
>arg2 : Base
>     : ^^^^
>r : Base
>  : ^^^^
>a : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>  : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^

declare function foo9(a: any): any;
>foo9 : { (a: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived): (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived; (a: any): any; }
>     : ^^^ ^^                                                                               ^^^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo10(a: (...x: Derived[]) => Derived): typeof a;
>foo10 : { (a: (...x: Derived[]) => Derived): typeof a; (a: any): any; }
>      : ^^^ ^^                            ^^^        ^^^ ^^   ^^^^^^^^^
>a : (...x: Derived[]) => Derived
>  : ^^^^ ^^         ^^^^^       
>x : Derived[]
>  : ^^^^^^^^^
>a : (...x: Derived[]) => Derived
>  : ^^^^ ^^         ^^^^^^^^^^^^

declare function foo10(a: any): any;
>foo10 : { (a: (...x: Derived[]) => Derived): (...x: Derived[]) => Derived; (a: any): any; }
>      : ^^^ ^^                            ^^^^^^^ ^^         ^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo11(a: (x: { foo: string }, y: { foo: string; bar: string }) => Base): typeof a;
>foo11 : { (a: (x: { foo: string; }, y: { foo: string; bar: string; }) => Base): typeof a; (a: any): any; }
>      : ^^^ ^^                                                               ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: { foo: string; }, y: { foo: string; bar: string; }) => Base
>  : ^ ^^                ^^ ^^                             ^^^^^    
>x : { foo: string; }
>  : ^^^^^^^      ^^^
>foo : string
>    : ^^^^^^
>y : { foo: string; bar: string; }
>  : ^^^^^^^      ^^^^^^^      ^^^
>foo : string
>    : ^^^^^^
>bar : string
>    : ^^^^^^
>a : (x: { foo: string; }, y: { foo: string; bar: string; }) => Base
>  : ^ ^^                ^^ ^^                             ^^^^^^^^^

declare function foo11(a: any): any;
>foo11 : { (a: (x: { foo: string; }, y: { foo: string; bar: string; }) => Base): (x: { foo: string; }, y: { foo: string; bar: string; }) => Base; (a: any): any; }
>      : ^^^ ^^                                                               ^^^^ ^^                ^^ ^^                             ^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo12(a: (x: Array<Base>, y: Array<Derived2>) => Array<Derived>): typeof a;
>foo12 : { (a: (x: Array<Base>, y: Array<Derived2>) => Array<Derived>): typeof a; (a: any): any; }
>      : ^^^ ^^                                                      ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: Array<Base>, y: Array<Derived2>) => Array<Derived>
>  : ^ ^^           ^^ ^^               ^^^^^              
>x : Base[]
>  : ^^^^^^
>y : Derived2[]
>  : ^^^^^^^^^^
>a : (x: Array<Base>, y: Array<Derived2>) => Derived[]
>  : ^ ^^           ^^ ^^               ^^^^^^^^^^^^^^

declare function foo12(a: any): any;
>foo12 : { (a: (x: Array<Base>, y: Array<Derived2>) => Array<Derived>): (x: Array<Base>, y: Array<Derived2>) => Derived[]; (a: any): any; }
>      : ^^^ ^^                                                      ^^^^ ^^           ^^ ^^               ^^^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo13(a: (x: Array<Base>, y: Array<Derived>) => Array<Derived>): typeof a;
>foo13 : { (a: (x: Array<Base>, y: Array<Derived>) => Array<Derived>): typeof a; (a: any): any; }
>      : ^^^ ^^                                                     ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: Array<Base>, y: Array<Derived>) => Array<Derived>
>  : ^ ^^           ^^ ^^              ^^^^^              
>x : Base[]
>  : ^^^^^^
>y : Derived[]
>  : ^^^^^^^^^
>a : (x: Array<Base>, y: Array<Derived>) => Derived[]
>  : ^ ^^           ^^ ^^              ^^^^^^^^^^^^^^

declare function foo13(a: any): any;
>foo13 : { (a: (x: Array<Base>, y: Array<Derived>) => Array<Derived>): (x: Array<Base>, y: Array<Derived>) => Derived[]; (a: any): any; }
>      : ^^^ ^^                                                     ^^^^ ^^           ^^ ^^              ^^^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo14(a: (x: { a: string; b: number }) => Object): typeof a;
>foo14 : { (a: (x: { a: string; b: number; }) => Object): typeof a; (a: any): any; }
>      : ^^^ ^^                                        ^^^        ^^^ ^^   ^^^^^^^^^
>a : (x: { a: string; b: number; }) => Object
>  : ^ ^^                         ^^^^^      
>x : { a: string; b: number; }
>  : ^^^^^      ^^^^^      ^^^
>a : string
>  : ^^^^^^
>b : number
>  : ^^^^^^
>a : (x: { a: string; b: number; }) => Object
>  : ^ ^^                         ^^^^^^^^^^^

declare function foo14(a: any): any;
>foo14 : { (a: (x: { a: string; b: number; }) => Object): (x: { a: string; b: number; }) => Object; (a: any): any; }
>      : ^^^ ^^                                        ^^^^ ^^                         ^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo15(a: { 
>foo15 : { (a: { (x: number): number[]; (x: string): string[]; }): typeof a; (a: any): any; }
>      : ^^^ ^^                                                 ^^^        ^^^ ^^   ^^^^^^^^^
>a : { (x: number): number[]; (x: string): string[]; }
>  : ^^^ ^^      ^^^        ^^^ ^^      ^^^        ^^^

    (x: number): number[];
>x : number
>  : ^^^^^^

    (x: string): string[]; 
>x : string
>  : ^^^^^^

}): typeof a;
>a : { (x: number): number[]; (x: string): string[]; }
>  : ^^^ ^^      ^^^^^^^^^^^^^^ ^^      ^^^^^^^^^^^^^^

declare function foo15(a: any): any;
>foo15 : { (a: { (x: number): number[]; (x: string): string[]; }): { (x: number): number[]; (x: string): string[]; }; (a: any): any; }
>      : ^^^ ^^                                                 ^^^^^^ ^^      ^^^^^^^^^^^^^^ ^^      ^^^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo16(a: {
>foo16 : { (a: { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }): typeof a; (a: any): any; }
>      : ^^^ ^^                                                                          ^^^        ^^^ ^^   ^^^^^^^^^
>a : { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }
>  : ^^^ ^^^^^^^^^^^^^^^^^^ ^^ ^^^        ^^^ ^^^^^^^^^^^^^^^ ^^ ^^^        ^^^

    <T extends Derived>(x: T): number[];
>x : T
>  : ^

    <U extends Base>(x: U): number[];
>x : U
>  : ^

}): typeof a;
>a : { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }
>  : ^^^ ^^^^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^

declare function foo16(a: any): any;
>foo16 : { (a: { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }): { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }; (a: any): any; }
>      : ^^^ ^^                                                                          ^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo17(a: {
>foo17 : { (a: { (x: (a: number) => number): number[]; (x: (a: string) => string): string[]; }): typeof a; (a: any): any; }
>      : ^^^ ^^                                                                               ^^^        ^^^ ^^   ^^^^^^^^^
>a : { (x: (a: number) => number): number[]; (x: (a: string) => string): string[]; }
>  : ^^^ ^^                     ^^^        ^^^ ^^                     ^^^        ^^^

    (x: (a: number) => number): number[];
>x : (a: number) => number
>  : ^ ^^      ^^^^^      
>a : number
>  : ^^^^^^

    (x: (a: string) => string): string[];
>x : (a: string) => string
>  : ^ ^^      ^^^^^      
>a : string
>  : ^^^^^^

}): typeof a;
>a : { (x: (a: number) => number): number[]; (x: (a: string) => string): string[]; }
>  : ^^^ ^^                     ^^^^^^^^^^^^^^ ^^                     ^^^^^^^^^^^^^^

declare function foo17(a: any): any;
>foo17 : { (a: { (x: (a: number) => number): number[]; (x: (a: string) => string): string[]; }): { (x: (a: number) => number): number[]; (x: (a: string) => string): string[]; }; (a: any): any; }
>      : ^^^ ^^                                                                               ^^^^^^ ^^                     ^^^^^^^^^^^^^^ ^^                     ^^^^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

declare function foo18(a: {
>foo18 : { (a: { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }): typeof a; (a: any): any; }
>      : ^^^ ^^                                                                                                                       ^^^        ^^^ ^^   ^^^^^^^^^
>a : { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }
>  : ^^^ ^^                                             ^^^     ^^^ ^^                                           ^^^     ^^^

    (x: {
>x : { (a: number): number; (a: string): string; }
>  : ^^^ ^^      ^^^      ^^^ ^^      ^^^      ^^^

        (a: number): number;
>a : number
>  : ^^^^^^

        (a: string): string;
>a : string
>  : ^^^^^^

    }): any[];
    (x: {
>x : { (a: boolean): boolean; (a: Date): Date; }
>  : ^^^ ^^       ^^^       ^^^ ^^    ^^^    ^^^

        (a: boolean): boolean;
>a : boolean
>  : ^^^^^^^

        (a: Date): Date;
>a : Date
>  : ^^^^

    }): any[];
}): typeof a;
>a : { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }
>  : ^^^ ^^                                             ^^^^^^^^^^^ ^^                                           ^^^^^^^^^^^

declare function foo18(a: any): any;
>foo18 : { (a: { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }): { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }; (a: any): any; }
>      : ^^^ ^^                                                                                                                       ^^^^^^ ^^                                             ^^^^^^^^^^^ ^^                                           ^^^^^^^^^^^^^^ ^^   ^^^   ^^^
>a : any

var r1arg1 = <T>(x: T) => [x];
>r1arg1 : <T>(x: T) => T[]
>       : ^ ^^ ^^ ^^^^^^^^
><T>(x: T) => [x] : <T>(x: T) => T[]
>                 : ^ ^^ ^^ ^^^^^^^^
>x : T
>  : ^
>[x] : T[]
>    : ^^^
>x : T
>  : ^

var r1arg2 = (x: number) => [1];
>r1arg2 : (x: number) => number[]
>       : ^ ^^      ^^^^^^^^^^^^^
>(x: number) => [1] : (x: number) => number[]
>                   : ^ ^^      ^^^^^^^^^^^^^
>x : number
>  : ^^^^^^
>[1] : number[]
>    : ^^^^^^^^
>1 : 1
>  : ^

var r1 = foo1(r1arg1); // any, return types are not subtype of first overload
>r1 : (x: number) => number[]
>   : ^ ^^      ^^^^^^^^^^^^^
>foo1(r1arg1) : (x: number) => number[]
>             : ^ ^^      ^^^^^^^^^^^^^
>foo1 : { (a: (x: number) => number[]): (x: number) => number[]; (a: any): any; }
>     : ^^^ ^^                       ^^^^ ^^      ^^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r1arg1 : <T>(x: T) => T[]
>       : ^ ^^ ^^ ^^^^^^^^

var r1a = [r1arg2, r1arg1]; // generic signature, subtype in both directions
>r1a : ((x: number) => number[])[]
>    : ^^ ^^      ^^^^^^^^^^^^^^^^
>[r1arg2, r1arg1] : ((x: number) => number[])[]
>                 : ^^ ^^      ^^^^^^^^^^^^^^^^
>r1arg2 : (x: number) => number[]
>       : ^ ^^      ^^^^^^^^^^^^^
>r1arg1 : <T>(x: T) => T[]
>       : ^ ^^ ^^ ^^^^^^^^

var r1b = [r1arg1, r1arg2]; // generic signature, subtype in both directions
>r1b : ((x: number) => number[])[]
>    : ^^ ^^      ^^^^^^^^^^^^^^^^
>[r1arg1, r1arg2] : ((x: number) => number[])[]
>                 : ^^ ^^      ^^^^^^^^^^^^^^^^
>r1arg1 : <T>(x: T) => T[]
>       : ^ ^^ ^^ ^^^^^^^^
>r1arg2 : (x: number) => number[]
>       : ^ ^^      ^^^^^^^^^^^^^

var r2arg1 = <T>(x: T) => [''];
>r2arg1 : <T>(x: T) => string[]
>       : ^ ^^ ^^ ^^^^^^^^^^^^^
><T>(x: T) => [''] : <T>(x: T) => string[]
>                  : ^ ^^ ^^ ^^^^^^^^^^^^^
>x : T
>  : ^
>[''] : string[]
>     : ^^^^^^^^
>'' : ""
>   : ^^

var r2arg2 = (x: number) => [''];
>r2arg2 : (x: number) => string[]
>       : ^ ^^      ^^^^^^^^^^^^^
>(x: number) => [''] : (x: number) => string[]
>                    : ^ ^^      ^^^^^^^^^^^^^
>x : number
>  : ^^^^^^
>[''] : string[]
>     : ^^^^^^^^
>'' : ""
>   : ^^

var r2 = foo2(r2arg1); 
>r2 : (x: number) => string[]
>   : ^ ^^      ^^^^^^^^^^^^^
>foo2(r2arg1) : (x: number) => string[]
>             : ^ ^^      ^^^^^^^^^^^^^
>foo2 : { (a: (x: number) => string[]): (x: number) => string[]; (a: any): any; }
>     : ^^^ ^^                       ^^^^ ^^      ^^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r2arg1 : <T>(x: T) => string[]
>       : ^ ^^ ^^ ^^^^^^^^^^^^^

var r2a = [r2arg1, r2arg2];
>r2a : ((x: number) => string[])[]
>    : ^^ ^^      ^^^^^^^^^^^^^^^^
>[r2arg1, r2arg2] : ((x: number) => string[])[]
>                 : ^^ ^^      ^^^^^^^^^^^^^^^^
>r2arg1 : <T>(x: T) => string[]
>       : ^ ^^ ^^ ^^^^^^^^^^^^^
>r2arg2 : (x: number) => string[]
>       : ^ ^^      ^^^^^^^^^^^^^

var r2b = [r2arg2, r2arg1];
>r2b : ((x: number) => string[])[]
>    : ^^ ^^      ^^^^^^^^^^^^^^^^
>[r2arg2, r2arg1] : ((x: number) => string[])[]
>                 : ^^ ^^      ^^^^^^^^^^^^^^^^
>r2arg2 : (x: number) => string[]
>       : ^ ^^      ^^^^^^^^^^^^^
>r2arg1 : <T>(x: T) => string[]
>       : ^ ^^ ^^ ^^^^^^^^^^^^^

var r3arg1 = <T>(x: T) => x;
>r3arg1 : <T>(x: T) => T
>       : ^ ^^ ^^ ^^^^^^
><T>(x: T) => x : <T>(x: T) => T
>               : ^ ^^ ^^ ^^^^^^
>x : T
>  : ^
>x : T
>  : ^

var r3arg2 = (x: number) => { };
>r3arg2 : (x: number) => void
>       : ^ ^^      ^^^^^^^^^
>(x: number) => { } : (x: number) => void
>                   : ^ ^^      ^^^^^^^^^
>x : number
>  : ^^^^^^

var r3 = foo3(r3arg1); 
>r3 : (x: number) => void
>   : ^ ^^      ^^^^^^^^^
>foo3(r3arg1) : (x: number) => void
>             : ^ ^^      ^^^^^^^^^
>foo3 : { (a: (x: number) => void): (x: number) => void; (a: any): any; }
>     : ^^^ ^^                   ^^^^ ^^      ^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r3arg1 : <T>(x: T) => T
>       : ^ ^^ ^^ ^^^^^^

var r3a = [r3arg1, r3arg2];
>r3a : ((x: number) => void)[]
>    : ^^ ^^      ^^^^^^^^^^^^
>[r3arg1, r3arg2] : ((x: number) => void)[]
>                 : ^^ ^^      ^^^^^^^^^^^^
>r3arg1 : <T>(x: T) => T
>       : ^ ^^ ^^ ^^^^^^
>r3arg2 : (x: number) => void
>       : ^ ^^      ^^^^^^^^^

var r3b = [r3arg2, r3arg1];
>r3b : ((x: number) => void)[]
>    : ^^ ^^      ^^^^^^^^^^^^
>[r3arg2, r3arg1] : ((x: number) => void)[]
>                 : ^^ ^^      ^^^^^^^^^^^^
>r3arg2 : (x: number) => void
>       : ^ ^^      ^^^^^^^^^
>r3arg1 : <T>(x: T) => T
>       : ^ ^^ ^^ ^^^^^^

var r4arg1 = <T, U>(x: T, y: U) => x;
>r4arg1 : <T, U>(x: T, y: U) => T
>       : ^ ^^ ^^ ^^ ^^ ^^ ^^^^^^
><T, U>(x: T, y: U) => x : <T, U>(x: T, y: U) => T
>                        : ^ ^^ ^^ ^^ ^^ ^^ ^^^^^^
>x : T
>  : ^
>y : U
>  : ^
>x : T
>  : ^

var r4arg2 = (x: string, y: number) => '';
>r4arg2 : (x: string, y: number) => string
>       : ^ ^^      ^^ ^^      ^^^^^^^^^^^
>(x: string, y: number) => '' : (x: string, y: number) => string
>                             : ^ ^^      ^^ ^^      ^^^^^^^^^^^
>x : string
>  : ^^^^^^
>y : number
>  : ^^^^^^
>'' : ""
>   : ^^

var r4 = foo4(r4arg1); // any
>r4 : (x: string, y: number) => string
>   : ^ ^^      ^^ ^^      ^^^^^^^^^^^
>foo4(r4arg1) : (x: string, y: number) => string
>             : ^ ^^      ^^ ^^      ^^^^^^^^^^^
>foo4 : { (a: (x: string, y: number) => string): (x: string, y: number) => string; (a: any): any; }
>     : ^^^ ^^                                ^^^^ ^^      ^^ ^^      ^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r4arg1 : <T, U>(x: T, y: U) => T
>       : ^ ^^ ^^ ^^ ^^ ^^ ^^^^^^

var r4a = [r4arg1, r4arg2];
>r4a : ((x: string, y: number) => string)[]
>    : ^^ ^^      ^^ ^^      ^^^^^^^^^^^^^^
>[r4arg1, r4arg2] : ((x: string, y: number) => string)[]
>                 : ^^ ^^      ^^ ^^      ^^^^^^^^^^^^^^
>r4arg1 : <T, U>(x: T, y: U) => T
>       : ^ ^^ ^^ ^^ ^^ ^^ ^^^^^^
>r4arg2 : (x: string, y: number) => string
>       : ^ ^^      ^^ ^^      ^^^^^^^^^^^

var r4b = [r4arg2, r4arg1];
>r4b : ((x: string, y: number) => string)[]
>    : ^^ ^^      ^^ ^^      ^^^^^^^^^^^^^^
>[r4arg2, r4arg1] : ((x: string, y: number) => string)[]
>                 : ^^ ^^      ^^ ^^      ^^^^^^^^^^^^^^
>r4arg2 : (x: string, y: number) => string
>       : ^ ^^      ^^ ^^      ^^^^^^^^^^^
>r4arg1 : <T, U>(x: T, y: U) => T
>       : ^ ^^ ^^ ^^ ^^ ^^ ^^^^^^

var r5arg1 = <T, U>(x: (arg: T) => U) => <T>null;
>r5arg1 : <T, U>(x: (arg: T) => U) => T
>       : ^ ^^ ^^ ^^             ^^^^^ 
><T, U>(x: (arg: T) => U) => <T>null : <T, U>(x: (arg: T) => U) => T
>                                    : ^ ^^ ^^ ^^             ^^^^^ 
>x : (arg: T) => U
>  : ^   ^^ ^^^^^ 
>arg : T
>    : ^
><T>null : T
>        : ^

var r5arg2 = (x: (arg: string) => number) => '';
>r5arg2 : (x: (arg: string) => number) => string
>       : ^ ^^                       ^^^^^^^^^^^
>(x: (arg: string) => number) => '' : (x: (arg: string) => number) => string
>                                   : ^ ^^                       ^^^^^^^^^^^
>x : (arg: string) => number
>  : ^   ^^      ^^^^^      
>arg : string
>    : ^^^^^^
>'' : ""
>   : ^^

var r5 = foo5(r5arg1); // any
>r5 : (x: (arg: string) => number) => string
>   : ^ ^^                       ^^^^^^^^^^^
>foo5(r5arg1) : (x: (arg: string) => number) => string
>             : ^ ^^                       ^^^^^^^^^^^
>foo5 : { (a: (x: (arg: string) => number) => string): (x: (arg: string) => number) => string; (a: any): any; }
>     : ^^^ ^^                                      ^^^^ ^^                       ^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r5arg1 : <T, U>(x: (arg: T) => U) => T
>       : ^ ^^ ^^ ^^             ^^^^^ 

var r5a = [r5arg1, r5arg2];
>r5a : ((x: (arg: string) => number) => string)[]
>    : ^^ ^^                       ^^^^^^^^^^^^^^
>[r5arg1, r5arg2] : ((x: (arg: string) => number) => string)[]
>                 : ^^ ^^                       ^^^^^^^^^^^^^^
>r5arg1 : <T, U>(x: (arg: T) => U) => T
>       : ^ ^^ ^^ ^^             ^^^^^ 
>r5arg2 : (x: (arg: string) => number) => string
>       : ^ ^^                       ^^^^^^^^^^^

var r5b = [r5arg2, r5arg1];
>r5b : ((x: (arg: string) => number) => string)[]
>    : ^^ ^^                       ^^^^^^^^^^^^^^
>[r5arg2, r5arg1] : ((x: (arg: string) => number) => string)[]
>                 : ^^ ^^                       ^^^^^^^^^^^^^^
>r5arg2 : (x: (arg: string) => number) => string
>       : ^ ^^                       ^^^^^^^^^^^
>r5arg1 : <T, U>(x: (arg: T) => U) => T
>       : ^ ^^ ^^ ^^             ^^^^^ 

var r6arg1 = <T extends Base, U extends Derived>(x: (arg: T) => U) => <T>null;
>r6arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U) => T
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^ 
><T extends Base, U extends Derived>(x: (arg: T) => U) => <T>null : <T extends Base, U extends Derived>(x: (arg: T) => U) => T
>                                                                 : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^ 
>x : (arg: T) => U
>  : ^   ^^ ^^^^^ 
>arg : T
>    : ^
><T>null : T
>        : ^

var r6arg2 = (x: (arg: Base) => Derived) => <Base>null;
>r6arg2 : (x: (arg: Base) => Derived) => Base
>       : ^ ^^                      ^^^^^    
>(x: (arg: Base) => Derived) => <Base>null : (x: (arg: Base) => Derived) => Base
>                                          : ^ ^^                      ^^^^^    
>x : (arg: Base) => Derived
>  : ^   ^^    ^^^^^       
>arg : Base
>    : ^^^^
><Base>null : Base
>           : ^^^^

var r6 = foo6(r6arg1); // any
>r6 : (x: (arg: Base) => Derived) => Base
>   : ^ ^^                      ^^^^^^^^^
>foo6(r6arg1) : (x: (arg: Base) => Derived) => Base
>             : ^ ^^                      ^^^^^^^^^
>foo6 : { (a: (x: (arg: Base) => Derived) => Base): (x: (arg: Base) => Derived) => Base; (a: any): any; }
>     : ^^^ ^^                                   ^^^^ ^^                      ^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r6arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U) => T
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^ 

var r6a = [r6arg1, r6arg2];
>r6a : ((x: (arg: Base) => Derived) => Base)[]
>    : ^^ ^^                      ^^^^^    ^^^
>[r6arg1, r6arg2] : ((x: (arg: Base) => Derived) => Base)[]
>                 : ^^ ^^                      ^^^^^    ^^^
>r6arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U) => T
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^ 
>r6arg2 : (x: (arg: Base) => Derived) => Base
>       : ^ ^^                      ^^^^^    

var r6b = [r6arg2, r6arg1];
>r6b : ((x: (arg: Base) => Derived) => Base)[]
>    : ^^ ^^                      ^^^^^    ^^^
>[r6arg2, r6arg1] : ((x: (arg: Base) => Derived) => Base)[]
>                 : ^^ ^^                      ^^^^^    ^^^
>r6arg2 : (x: (arg: Base) => Derived) => Base
>       : ^ ^^                      ^^^^^    
>r6arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U) => T
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^ 

var r7arg1 = <T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => <U>null;
>r7arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^^ ^^ ^^^^^ 
><T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => <U>null : <T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => U
>                                                                           : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^^ ^^ ^^^^^ 
>x : (arg: T) => U
>  : ^   ^^ ^^^^^ 
>arg : T
>    : ^
>(r: T) => <U>null : (r: T) => U
>                  : ^ ^^ ^^^^^ 
>r : T
>  : ^
><U>null : U
>        : ^

var r7arg2 = (x: (arg: Base) => Derived) => (r: Base) => <Derived>null;
>r7arg2 : (x: (arg: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^^^^^ ^^    ^^^^^       
>(x: (arg: Base) => Derived) => (r: Base) => <Derived>null : (x: (arg: Base) => Derived) => (r: Base) => Derived
>                                                          : ^ ^^                      ^^^^^^ ^^    ^^^^^       
>x : (arg: Base) => Derived
>  : ^   ^^    ^^^^^       
>arg : Base
>    : ^^^^
>(r: Base) => <Derived>null : (r: Base) => Derived
>                           : ^ ^^    ^^^^^       
>r : Base
>  : ^^^^
><Derived>null : Derived
>              : ^^^^^^^

var r7 = foo7(r7arg1); // any
>r7 : (x: (arg: Base) => Derived) => (r: Base) => Derived
>   : ^ ^^                      ^^^^^^ ^^    ^^^^^^^^^^^^
>foo7(r7arg1) : (x: (arg: Base) => Derived) => (r: Base) => Derived
>             : ^ ^^                      ^^^^^^ ^^    ^^^^^^^^^^^^
>foo7 : { (a: (x: (arg: Base) => Derived) => (r: Base) => Derived): (x: (arg: Base) => Derived) => (r: Base) => Derived; (a: any): any; }
>     : ^^^ ^^                                                   ^^^^ ^^                      ^^^^^^ ^^    ^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r7arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^^ ^^ ^^^^^ 

var r7a = [r7arg1, r7arg2];
>r7a : ((x: (arg: Base) => Derived) => (r: Base) => Derived)[]
>    : ^^ ^^                      ^^^^^^ ^^    ^^^^^       ^^^
>[r7arg1, r7arg2] : ((x: (arg: Base) => Derived) => (r: Base) => Derived)[]
>                 : ^^ ^^                      ^^^^^^ ^^    ^^^^^       ^^^
>r7arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^^ ^^ ^^^^^ 
>r7arg2 : (x: (arg: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^^^^^ ^^    ^^^^^       

var r7b = [r7arg2, r7arg1];
>r7b : ((x: (arg: Base) => Derived) => (r: Base) => Derived)[]
>    : ^^ ^^                      ^^^^^^ ^^    ^^^^^       ^^^
>[r7arg2, r7arg1] : ((x: (arg: Base) => Derived) => (r: Base) => Derived)[]
>                 : ^^ ^^                      ^^^^^^ ^^    ^^^^^       ^^^
>r7arg2 : (x: (arg: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^^^^^ ^^    ^^^^^       
>r7arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^^^^^ ^^ ^^^^^ 

var r8arg1 = <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => <U>null;
>r8arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^              ^^^^^^ ^^ ^^^^^ 
><T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => <U>null : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => U
>                                                                                              : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^              ^^^^^^ ^^ ^^^^^ 
>x : (arg: T) => U
>  : ^   ^^ ^^^^^ 
>arg : T
>    : ^
>y : (arg2: T) => U
>  : ^    ^^ ^^^^^ 
>arg2 : T
>     : ^
>(r: T) => <U>null : (r: T) => U
>                  : ^ ^^ ^^^^^ 
>r : T
>  : ^
><U>null : U
>        : ^

var r8arg2 = (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => <Derived>null;
>r8arg2 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       
>(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => <Derived>null : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>                                                                                      : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       
>x : (arg: Base) => Derived
>  : ^   ^^    ^^^^^       
>arg : Base
>    : ^^^^
>y : (arg2: Base) => Derived
>  : ^    ^^    ^^^^^       
>arg2 : Base
>     : ^^^^
>(r: Base) => <Derived>null : (r: Base) => Derived
>                           : ^ ^^    ^^^^^       
>r : Base
>  : ^^^^
><Derived>null : Derived
>              : ^^^^^^^

var r8 = foo8(r8arg1); // any
>r8 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>   : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^
>foo8(r8arg1) : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>             : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^
>foo8 : { (a: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived): (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived; (a: any): any; }
>     : ^^^ ^^                                                                               ^^^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r8arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^              ^^^^^^ ^^ ^^^^^ 

var r8a = [r8arg1, r8arg2];
>r8a : ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived)[]
>    : ^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       ^^^
>[r8arg1, r8arg2] : ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived)[]
>                 : ^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       ^^^
>r8arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^              ^^^^^^ ^^ ^^^^^ 
>r8arg2 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       

var r8b = [r8arg2, r8arg1];
>r8b : ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived)[]
>    : ^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       ^^^
>[r8arg2, r8arg1] : ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived)[]
>                 : ^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       ^^^
>r8arg2 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       
>r8arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: T) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^              ^^^^^^ ^^ ^^^^^ 

var r9arg1 = <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number }) => U) => (r: T) => <U>null;
>r9arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^                                           ^^^^^^ ^^ ^^^^^ 
><T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number }) => U) => (r: T) => <U>null : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U
>                                                                                                                          : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^                                           ^^^^^^ ^^ ^^^^^ 
>x : (arg: T) => U
>  : ^   ^^ ^^^^^ 
>arg : T
>    : ^
>y : (arg2: { foo: string; bing: number; }) => U
>  : ^    ^^                              ^^^^^ 
>arg2 : { foo: string; bing: number; }
>     : ^^^^^^^      ^^^^^^^^      ^^^
>foo : string
>    : ^^^^^^
>bing : number
>     : ^^^^^^
>(r: T) => <U>null : (r: T) => U
>                  : ^ ^^ ^^^^^ 
>r : T
>  : ^
><U>null : U
>        : ^

var r9arg2 = (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => <Derived>null;
>r9arg2 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       
>(x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => <Derived>null : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>                                                                                      : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       
>x : (arg: Base) => Derived
>  : ^   ^^    ^^^^^       
>arg : Base
>    : ^^^^
>y : (arg2: Base) => Derived
>  : ^    ^^    ^^^^^       
>arg2 : Base
>     : ^^^^
>(r: Base) => <Derived>null : (r: Base) => Derived
>                           : ^ ^^    ^^^^^       
>r : Base
>  : ^^^^
><Derived>null : Derived
>              : ^^^^^^^

var r9 = foo9(r9arg1); // any
>r9 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>   : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^
>foo9(r9arg1) : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>             : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^
>foo9 : { (a: (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived): (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived; (a: any): any; }
>     : ^^^ ^^                                                                               ^^^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r9arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^                                           ^^^^^^ ^^ ^^^^^ 

var r9a = [r9arg1, r9arg2];
>r9a : ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived)[]
>    : ^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       ^^^
>[r9arg1, r9arg2] : ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived)[]
>                 : ^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       ^^^
>r9arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^                                           ^^^^^^ ^^ ^^^^^ 
>r9arg2 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       

var r9b = [r9arg2, r9arg1];
>r9b : ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived)[]
>    : ^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       ^^^
>[r9arg2, r9arg1] : ((x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived)[]
>                 : ^^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       ^^^
>r9arg2 : (x: (arg: Base) => Derived, y: (arg2: Base) => Derived) => (r: Base) => Derived
>       : ^ ^^                      ^^ ^^                       ^^^^^^ ^^    ^^^^^       
>r9arg1 : <T extends Base, U extends Derived>(x: (arg: T) => U, y: (arg2: { foo: string; bing: number; }) => U) => (r: T) => U
>       : ^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^             ^^ ^^                                           ^^^^^^ ^^ ^^^^^ 

var r10arg1 = <T extends Derived>(...x: T[]) => x[0];
>r10arg1 : <T extends Derived>(...x: T[]) => T
>        : ^ ^^^^^^^^^^^^^^^^^^^^^ ^^   ^^^^^^
><T extends Derived>(...x: T[]) => x[0] : <T extends Derived>(...x: T[]) => T
>                                       : ^ ^^^^^^^^^^^^^^^^^^^^^ ^^   ^^^^^^
>x : T[]
>  : ^^^
>x[0] : T
>     : ^
>x : T[]
>  : ^^^
>0 : 0
>  : ^

var r10arg2 = (...x: Derived[]) => <Derived>null;
>r10arg2 : (...x: Derived[]) => Derived
>        : ^^^^ ^^         ^^^^^       
>(...x: Derived[]) => <Derived>null : (...x: Derived[]) => Derived
>                                   : ^^^^ ^^         ^^^^^       
>x : Derived[]
>  : ^^^^^^^^^
><Derived>null : Derived
>              : ^^^^^^^

var r10 = foo10(r10arg1); // any
>r10 : (...x: Derived[]) => Derived
>    : ^^^^ ^^         ^^^^^^^^^^^^
>foo10(r10arg1) : (...x: Derived[]) => Derived
>               : ^^^^ ^^         ^^^^^^^^^^^^
>foo10 : { (a: (...x: Derived[]) => Derived): (...x: Derived[]) => Derived; (a: any): any; }
>      : ^^^ ^^                            ^^^^^^^ ^^         ^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r10arg1 : <T extends Derived>(...x: T[]) => T
>        : ^ ^^^^^^^^^^^^^^^^^^^^^ ^^   ^^^^^^

var r10a = [r10arg1, r10arg2];
>r10a : ((...x: Derived[]) => Derived)[]
>     : ^^^^^ ^^         ^^^^^       ^^^
>[r10arg1, r10arg2] : ((...x: Derived[]) => Derived)[]
>                   : ^^^^^ ^^         ^^^^^       ^^^
>r10arg1 : <T extends Derived>(...x: T[]) => T
>        : ^ ^^^^^^^^^^^^^^^^^^^^^ ^^   ^^^^^^
>r10arg2 : (...x: Derived[]) => Derived
>        : ^^^^ ^^         ^^^^^       

var r10b = [r10arg2, r10arg1];
>r10b : ((...x: Derived[]) => Derived)[]
>     : ^^^^^ ^^         ^^^^^       ^^^
>[r10arg2, r10arg1] : ((...x: Derived[]) => Derived)[]
>                   : ^^^^^ ^^         ^^^^^       ^^^
>r10arg2 : (...x: Derived[]) => Derived
>        : ^^^^ ^^         ^^^^^       
>r10arg1 : <T extends Derived>(...x: T[]) => T
>        : ^ ^^^^^^^^^^^^^^^^^^^^^ ^^   ^^^^^^

var r11arg1 = <T extends Base>(x: T, y: T) => x;
>r11arg1 : <T extends Base>(x: T, y: T) => T
>        : ^ ^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^^^^^
><T extends Base>(x: T, y: T) => x : <T extends Base>(x: T, y: T) => T
>                                  : ^ ^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^^^^^
>x : T
>  : ^
>y : T
>  : ^
>x : T
>  : ^

var r11arg2 = (x: { foo: string }, y: { foo: string; bar: string }) => <Base>null;
>r11arg2 : (x: { foo: string; }, y: { foo: string; bar: string; }) => Base
>        : ^ ^^                ^^ ^^                             ^^^^^    
>(x: { foo: string }, y: { foo: string; bar: string }) => <Base>null : (x: { foo: string; }, y: { foo: string; bar: string; }) => Base
>                                                                    : ^ ^^                ^^ ^^                             ^^^^^    
>x : { foo: string; }
>  : ^^^^^^^      ^^^
>foo : string
>    : ^^^^^^
>y : { foo: string; bar: string; }
>  : ^^^^^^^      ^^^^^^^      ^^^
>foo : string
>    : ^^^^^^
>bar : string
>    : ^^^^^^
><Base>null : Base
>           : ^^^^

var r11 = foo11(r11arg1); // any
>r11 : (x: { foo: string; }, y: { foo: string; bar: string; }) => Base
>    : ^ ^^                ^^ ^^                             ^^^^^^^^^
>foo11(r11arg1) : (x: { foo: string; }, y: { foo: string; bar: string; }) => Base
>               : ^ ^^                ^^ ^^                             ^^^^^^^^^
>foo11 : { (a: (x: { foo: string; }, y: { foo: string; bar: string; }) => Base): (x: { foo: string; }, y: { foo: string; bar: string; }) => Base; (a: any): any; }
>      : ^^^ ^^                                                               ^^^^ ^^                ^^ ^^                             ^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r11arg1 : <T extends Base>(x: T, y: T) => T
>        : ^ ^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^^^^^

var r11a = [r11arg1, r11arg2];
>r11a : ((x: { foo: string; }, y: { foo: string; bar: string; }) => Base)[]
>     : ^^ ^^                ^^ ^^                             ^^^^^    ^^^
>[r11arg1, r11arg2] : ((x: { foo: string; }, y: { foo: string; bar: string; }) => Base)[]
>                   : ^^ ^^                ^^ ^^                             ^^^^^    ^^^
>r11arg1 : <T extends Base>(x: T, y: T) => T
>        : ^ ^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^^^^^
>r11arg2 : (x: { foo: string; }, y: { foo: string; bar: string; }) => Base
>        : ^ ^^                ^^ ^^                             ^^^^^    

var r11b = [r11arg2, r11arg1];
>r11b : ((x: { foo: string; }, y: { foo: string; bar: string; }) => Base)[]
>     : ^^ ^^                ^^ ^^                             ^^^^^    ^^^
>[r11arg2, r11arg1] : ((x: { foo: string; }, y: { foo: string; bar: string; }) => Base)[]
>                   : ^^ ^^                ^^ ^^                             ^^^^^    ^^^
>r11arg2 : (x: { foo: string; }, y: { foo: string; bar: string; }) => Base
>        : ^ ^^                ^^ ^^                             ^^^^^    
>r11arg1 : <T extends Base>(x: T, y: T) => T
>        : ^ ^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^^^^^

var r12arg1 = <T extends Array<Base>>(x: Array<Base>, y: T) => <Array<Derived>>null;
>r12arg1 : <T extends Base[]>(x: Array<Base>, y: T) => Array<Derived>
>        : ^ ^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^              
><T extends Array<Base>>(x: Array<Base>, y: T) => <Array<Derived>>null : <T extends Base[]>(x: Array<Base>, y: T) => Array<Derived>
>                                                                      : ^ ^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^              
>x : Base[]
>  : ^^^^^^
>y : T
>  : ^
><Array<Derived>>null : Derived[]
>                     : ^^^^^^^^^

var r12arg2 = (x: Array<Base>, y: Array<Derived2>) => <Array<Derived>>null;
>r12arg2 : (x: Array<Base>, y: Array<Derived2>) => Array<Derived>
>        : ^ ^^           ^^ ^^               ^^^^^              
>(x: Array<Base>, y: Array<Derived2>) => <Array<Derived>>null : (x: Array<Base>, y: Array<Derived2>) => Array<Derived>
>                                                             : ^ ^^           ^^ ^^               ^^^^^              
>x : Base[]
>  : ^^^^^^
>y : Derived2[]
>  : ^^^^^^^^^^
><Array<Derived>>null : Derived[]
>                     : ^^^^^^^^^

var r12 = foo12(r12arg1); // any
>r12 : (x: Array<Base>, y: Array<Derived2>) => Derived[]
>    : ^ ^^           ^^ ^^               ^^^^^^^^^^^^^^
>foo12(r12arg1) : (x: Array<Base>, y: Array<Derived2>) => Derived[]
>               : ^ ^^           ^^ ^^               ^^^^^^^^^^^^^^
>foo12 : { (a: (x: Array<Base>, y: Array<Derived2>) => Array<Derived>): (x: Array<Base>, y: Array<Derived2>) => Derived[]; (a: any): any; }
>      : ^^^ ^^                                                      ^^^^ ^^           ^^ ^^               ^^^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r12arg1 : <T extends Base[]>(x: Array<Base>, y: T) => Array<Derived>
>        : ^ ^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^              

var r12a = [r12arg1, r12arg2];
>r12a : ((x: Array<Base>, y: Array<Derived2>) => Array<Derived>)[]
>     : ^^ ^^           ^^ ^^               ^^^^^              ^^^
>[r12arg1, r12arg2] : ((x: Array<Base>, y: Array<Derived2>) => Array<Derived>)[]
>                   : ^^ ^^           ^^ ^^               ^^^^^              ^^^
>r12arg1 : <T extends Base[]>(x: Array<Base>, y: T) => Array<Derived>
>        : ^ ^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^              
>r12arg2 : (x: Array<Base>, y: Array<Derived2>) => Array<Derived>
>        : ^ ^^           ^^ ^^               ^^^^^              

var r12b = [r12arg2, r12arg1];
>r12b : ((x: Array<Base>, y: Array<Derived2>) => Array<Derived>)[]
>     : ^^ ^^           ^^ ^^               ^^^^^              ^^^
>[r12arg2, r12arg1] : ((x: Array<Base>, y: Array<Derived2>) => Array<Derived>)[]
>                   : ^^ ^^           ^^ ^^               ^^^^^              ^^^
>r12arg2 : (x: Array<Base>, y: Array<Derived2>) => Array<Derived>
>        : ^ ^^           ^^ ^^               ^^^^^              
>r12arg1 : <T extends Base[]>(x: Array<Base>, y: T) => Array<Derived>
>        : ^ ^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^              

var r13arg1 = <T extends Array<Derived>>(x: Array<Base>, y: T) => y;
>r13arg1 : <T extends Derived[]>(x: Array<Base>, y: T) => T
>        : ^ ^^^^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^^
><T extends Array<Derived>>(x: Array<Base>, y: T) => y : <T extends Derived[]>(x: Array<Base>, y: T) => T
>                                                      : ^ ^^^^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^^
>x : Base[]
>  : ^^^^^^
>y : T
>  : ^
>y : T
>  : ^

var r13arg2 = (x: Array<Base>, y: Array<Derived>) => <Array<Derived>>null;
>r13arg2 : (x: Array<Base>, y: Array<Derived>) => Array<Derived>
>        : ^ ^^           ^^ ^^              ^^^^^              
>(x: Array<Base>, y: Array<Derived>) => <Array<Derived>>null : (x: Array<Base>, y: Array<Derived>) => Array<Derived>
>                                                            : ^ ^^           ^^ ^^              ^^^^^              
>x : Base[]
>  : ^^^^^^
>y : Derived[]
>  : ^^^^^^^^^
><Array<Derived>>null : Derived[]
>                     : ^^^^^^^^^

var r13 = foo13(r13arg1); // any
>r13 : (x: Array<Base>, y: Array<Derived>) => Derived[]
>    : ^ ^^           ^^ ^^              ^^^^^^^^^^^^^^
>foo13(r13arg1) : (x: Array<Base>, y: Array<Derived>) => Derived[]
>               : ^ ^^           ^^ ^^              ^^^^^^^^^^^^^^
>foo13 : { (a: (x: Array<Base>, y: Array<Derived>) => Array<Derived>): (x: Array<Base>, y: Array<Derived>) => Derived[]; (a: any): any; }
>      : ^^^ ^^                                                     ^^^^ ^^           ^^ ^^              ^^^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r13arg1 : <T extends Derived[]>(x: Array<Base>, y: T) => T
>        : ^ ^^^^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^^

var r13a = [r13arg1, r13arg2];
>r13a : ((x: Array<Base>, y: Array<Derived>) => Array<Derived>)[]
>     : ^^ ^^           ^^ ^^              ^^^^^              ^^^
>[r13arg1, r13arg2] : ((x: Array<Base>, y: Array<Derived>) => Array<Derived>)[]
>                   : ^^ ^^           ^^ ^^              ^^^^^              ^^^
>r13arg1 : <T extends Derived[]>(x: Array<Base>, y: T) => T
>        : ^ ^^^^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^^
>r13arg2 : (x: Array<Base>, y: Array<Derived>) => Array<Derived>
>        : ^ ^^           ^^ ^^              ^^^^^              

var r13b = [r13arg2, r13arg1];
>r13b : ((x: Array<Base>, y: Array<Derived>) => Array<Derived>)[]
>     : ^^ ^^           ^^ ^^              ^^^^^              ^^^
>[r13arg2, r13arg1] : ((x: Array<Base>, y: Array<Derived>) => Array<Derived>)[]
>                   : ^^ ^^           ^^ ^^              ^^^^^              ^^^
>r13arg2 : (x: Array<Base>, y: Array<Derived>) => Array<Derived>
>        : ^ ^^           ^^ ^^              ^^^^^              
>r13arg1 : <T extends Derived[]>(x: Array<Base>, y: T) => T
>        : ^ ^^^^^^^^^^^^^^^^^^^^ ^^           ^^ ^^ ^^^^^^

var r14arg1 = <T>(x: { a: T; b: T }) => x.a;
>r14arg1 : <T>(x: { a: T; b: T; }) => T
>        : ^ ^^ ^^               ^^^^^^
><T>(x: { a: T; b: T }) => x.a : <T>(x: { a: T; b: T; }) => T
>                              : ^ ^^ ^^               ^^^^^^
>x : { a: T; b: T; }
>  : ^^^^^ ^^^^^ ^^^
>a : T
>  : ^
>b : T
>  : ^
>x.a : T
>    : ^
>x : { a: T; b: T; }
>  : ^^^^^^^^^^^^^^^
>a : T
>  : ^

var r14arg2 = (x: { a: string; b: number }) => <Object>null;
>r14arg2 : (x: { a: string; b: number; }) => Object
>        : ^ ^^                         ^^^^^      
>(x: { a: string; b: number }) => <Object>null : (x: { a: string; b: number; }) => Object
>                                              : ^ ^^                         ^^^^^      
>x : { a: string; b: number; }
>  : ^^^^^      ^^^^^      ^^^
>a : string
>  : ^^^^^^
>b : number
>  : ^^^^^^
><Object>null : Object
>             : ^^^^^^

var r14 = foo14(r14arg1); // any
>r14 : (x: { a: string; b: number; }) => Object
>    : ^ ^^                         ^^^^^^^^^^^
>foo14(r14arg1) : (x: { a: string; b: number; }) => Object
>               : ^ ^^                         ^^^^^^^^^^^
>foo14 : { (a: (x: { a: string; b: number; }) => Object): (x: { a: string; b: number; }) => Object; (a: any): any; }
>      : ^^^ ^^                                        ^^^^ ^^                         ^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r14arg1 : <T>(x: { a: T; b: T; }) => T
>        : ^ ^^ ^^               ^^^^^^

var r14a = [r14arg1, r14arg2];
>r14a : ((<T>(x: { a: T; b: T; }) => T) | ((x: { a: string; b: number; }) => Object))[]
>     : ^^^ ^^ ^^               ^^^^^^^^^^^^ ^^                         ^^^^^      ^^^^
>[r14arg1, r14arg2] : ((<T>(x: { a: T; b: T; }) => T) | ((x: { a: string; b: number; }) => Object))[]
>                   : ^^^ ^^ ^^               ^^^^^^^^^^^^ ^^                         ^^^^^      ^^^^
>r14arg1 : <T>(x: { a: T; b: T; }) => T
>        : ^ ^^ ^^               ^^^^^^
>r14arg2 : (x: { a: string; b: number; }) => Object
>        : ^ ^^                         ^^^^^      

var r14b = [r14arg2, r14arg1];
>r14b : ((<T>(x: { a: T; b: T; }) => T) | ((x: { a: string; b: number; }) => Object))[]
>     : ^^^ ^^ ^^               ^^^^^^^^^^^^ ^^                         ^^^^^      ^^^^
>[r14arg2, r14arg1] : ((<T>(x: { a: T; b: T; }) => T) | ((x: { a: string; b: number; }) => Object))[]
>                   : ^^^ ^^ ^^               ^^^^^^^^^^^^ ^^                         ^^^^^      ^^^^
>r14arg2 : (x: { a: string; b: number; }) => Object
>        : ^ ^^                         ^^^^^      
>r14arg1 : <T>(x: { a: T; b: T; }) => T
>        : ^ ^^ ^^               ^^^^^^

var r15arg1 = <T>(x: T) => <T[]>null
>r15arg1 : <T>(x: T) => T[]
>        : ^ ^^ ^^ ^^^^^   
><T>(x: T) => <T[]>null : <T>(x: T) => T[]
>                       : ^ ^^ ^^ ^^^^^   
>x : T
>  : ^
><T[]>null : T[]
>          : ^^^

var r15 = foo15(r15arg1); // any
>r15 : any
>foo15(r15arg1) : any
>foo15 : { (a: { (x: number): number[]; (x: string): string[]; }): { (x: number): number[]; (x: string): string[]; }; (a: any): any; }
>      : ^^^ ^^                                                 ^^^^^^ ^^      ^^^^^^^^^^^^^^ ^^      ^^^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r15arg1 : <T>(x: T) => T[]
>        : ^ ^^ ^^ ^^^^^   

var r16arg1 = <T extends Base>(x: T) => [1];
>r16arg1 : <T extends Base>(x: T) => number[]
>        : ^ ^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^
><T extends Base>(x: T) => [1] : <T extends Base>(x: T) => number[]
>                              : ^ ^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^
>x : T
>  : ^
>[1] : number[]
>    : ^^^^^^^^
>1 : 1
>  : ^

var r16 = foo16(r16arg1); 
>r16 : { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }
>    : ^^^ ^^^^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^
>foo16(r16arg1) : { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }
>               : ^^^ ^^^^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^
>foo16 : { (a: { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }): { <T extends Derived>(x: T): number[]; <U extends Base>(x: U): number[]; }; (a: any): any; }
>      : ^^^ ^^                                                                          ^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r16arg1 : <T extends Base>(x: T) => number[]
>        : ^ ^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^

var r17arg1 = <T>(x: (a: T) => T) => <T[]>null;
>r17arg1 : <T>(x: (a: T) => T) => T[]
>        : ^ ^^ ^^           ^^^^^   
><T>(x: (a: T) => T) => <T[]>null : <T>(x: (a: T) => T) => T[]
>                                 : ^ ^^ ^^           ^^^^^   
>x : (a: T) => T
>  : ^ ^^ ^^^^^ 
>a : T
>  : ^
><T[]>null : T[]
>          : ^^^

var r17 = foo17(r17arg1); // any
>r17 : any
>foo17(r17arg1) : any
>foo17 : { (a: { (x: (a: number) => number): number[]; (x: (a: string) => string): string[]; }): { (x: (a: number) => number): number[]; (x: (a: string) => string): string[]; }; (a: any): any; }
>      : ^^^ ^^                                                                               ^^^^^^ ^^                     ^^^^^^^^^^^^^^ ^^                     ^^^^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r17arg1 : <T>(x: (a: T) => T) => T[]
>        : ^ ^^ ^^           ^^^^^   

var r18arg1 = <T>(x: (a: T) => T) => <T[]>null;
>r18arg1 : <T>(x: (a: T) => T) => T[]
>        : ^ ^^ ^^           ^^^^^   
><T>(x: (a: T) => T) => <T[]>null : <T>(x: (a: T) => T) => T[]
>                                 : ^ ^^ ^^           ^^^^^   
>x : (a: T) => T
>  : ^ ^^ ^^^^^ 
>a : T
>  : ^
><T[]>null : T[]
>          : ^^^

var r18 = foo18(r18arg1); 
>r18 : { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }
>    : ^^^ ^^                                             ^^^^^^^^^^^ ^^                                           ^^^^^^^^^^^
>foo18(r18arg1) : { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }
>               : ^^^ ^^                                             ^^^^^^^^^^^ ^^                                           ^^^^^^^^^^^
>foo18 : { (a: { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }): { (x: { (a: number): number; (a: string): string; }): any[]; (x: { (a: boolean): boolean; (a: Date): Date; }): any[]; }; (a: any): any; }
>      : ^^^ ^^                                                                                                                       ^^^^^^ ^^                                             ^^^^^^^^^^^ ^^                                           ^^^^^^^^^^^^^^ ^^   ^^^^^^^^^
>r18arg1 : <T>(x: (a: T) => T) => T[]
>        : ^ ^^ ^^           ^^^^^