//// [overloadResolution.ts] class SomeBase { private n; public s: string; } class SomeDerived1 extends SomeBase { private m; } class SomeDerived2 extends SomeBase { private m; } class SomeDerived3 extends SomeBase { private m; } // Ambiguous call picks the first overload in declaration order function fn1(s: string): string; function fn1(s: number): number; function fn1() { return null; } var s = fn1(undefined); var s: string; // No candidate overloads found fn1({}); // Error // Generic and non - generic overload where generic overload is the only candidate when called with type arguments function fn2(s: string, n: number): number; function fn2(n: number, t: T): T; function fn2() { return undefined; } var d = fn2(0, undefined); var d: Date; // Generic and non - generic overload where generic overload is the only candidate when called without type arguments var s = fn2(0, ''); // Generic and non - generic overload where non - generic overload is the only candidate when called with type arguments fn2('', 0); // Error // Generic and non - generic overload where non - generic overload is the only candidate when called without type arguments fn2('', 0); // OK // Generic overloads with differing arity called without type arguments function fn3(n: T): string; function fn3(s: string, t: T, u: U): U; function fn3(v: V, u: U, t: T): number; function fn3() { return null; } var s = fn3(3); var s = fn3('', 3, ''); var n = fn3(5, 5, 5); var n: number; // Generic overloads with differing arity called with type arguments matching each overload type parameter count var s = fn3(4); var s = fn3('', '', ''); var n = fn3('', '', 3); // Generic overloads with differing arity called with type argument count that doesn't match any overload fn3(); // Error // Generic overloads with constraints called with type arguments that satisfy the constraints function fn4(n: T, m: U); function fn4(n: T, m: U); function fn4() { } fn4('', 3); fn4(3, ''); // Error fn4('', 3); // Error fn4(3, ''); // Generic overloads with constraints called without type arguments but with types that satisfy the constraints fn4('', 3); fn4(3, ''); fn4(3, undefined); fn4('', null); // Generic overloads with constraints called with type arguments that do not satisfy the constraints fn4(null, null); // Error // Generic overloads with constraints called without type arguments but with types that do not satisfy the constraints fn4(true, null); // Error fn4(null, true); // Error // Non - generic overloads where contextual typing of function arguments has errors function fn5(f: (n: string) => void): string; function fn5(f: (n: number) => void): number; function fn5() { return undefined; } var n = fn5((n) => n.toFixed()); var s = fn5((n) => n.substr(0)); //// [overloadResolution.js] var __extends = this.__extends || function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; function __() { this.constructor = d; } __.prototype = b.prototype; d.prototype = new __(); }; var SomeBase = (function () { function SomeBase() { } return SomeBase; })(); var SomeDerived1 = (function (_super) { __extends(SomeDerived1, _super); function SomeDerived1() { _super.apply(this, arguments); } return SomeDerived1; })(SomeBase); var SomeDerived2 = (function (_super) { __extends(SomeDerived2, _super); function SomeDerived2() { _super.apply(this, arguments); } return SomeDerived2; })(SomeBase); var SomeDerived3 = (function (_super) { __extends(SomeDerived3, _super); function SomeDerived3() { _super.apply(this, arguments); } return SomeDerived3; })(SomeBase); function fn1() { return null; } var s = fn1(undefined); var s; fn1({}); function fn2() { return undefined; } var d = fn2(0, undefined); var d; // Generic and non - generic overload where generic overload is the only candidate when called without type arguments var s = fn2(0, ''); fn2('', 0); fn2('', 0); function fn3() { return null; } var s = fn3(3); var s = fn3('', 3, ''); var n = fn3(5, 5, 5); var n; // Generic overloads with differing arity called with type arguments matching each overload type parameter count var s = fn3(4); var s = fn3('', '', ''); var n = fn3('', '', 3); fn3(); function fn4() { } fn4('', 3); fn4(3, ''); fn4('', 3); fn4(3, ''); fn4('', 3); fn4(3, ''); fn4(3, undefined); fn4('', null); fn4(null, null); fn4(true, null); fn4(null, true); function fn5() { return undefined; } var n = fn5(function (n) { return n.toFixed(); }); var s = fn5(function (n) { return n.substr(0); });