// checking assignment compatibility relations for function types. All valid class Base { foo: string; } class Derived extends Base { bar: string; } class Derived2 extends Derived { baz: string; } class OtherDerived extends Base { bing: string; } interface A { a: (x: T) => T[]; a2: (x: T) => string[]; a3: (x: T) => void; a4: (x: T, y: U) => string; a5: (x: (arg: T) => U) => T; a6: (x: (arg: T) => Derived) => T; a11: (x: { foo: T }, y: { foo: T; bar: T }) => Base; a15: (x: { a: T; b: T }) => T[]; a16: (x: { a: T; b: T }) => T[]; } var x: A; var b: (x: T) => T[]; x.a = b; b = x.a; var b2: (x: T) => string[]; x.a2 = b2; b2 = x.a2; var b3: (x: T) => T; x.a3 = b3; b3 = x.a3; var b4: (x: T, y: U) => string; x.a4 = b4; b4 = x.a4; var b5: (x: (arg: T) => U) => T; x.a5 = b5; b5 = x.a5; var b11: (x: { foo: T }, y: { foo: U; bar: U }) => Base; x.a11 = b11; b11 = x.a11; var b16: (x: { a: T; b: T }) => T[]; x.a16 = b16; b16 = x.a16;