//// [apparentTypeSubtyping.ts] // subtype checks use the apparent type of the target type // S is a subtype of a type T, and T is a supertype of S, if one of the following is true, where S' denotes the apparent type (section 3.8.1) of S: class Base { x: U; } // is String (S) a subtype of U extends String (T)? Would only be true if we used the apparent type of U (T) class Derived extends Base { // error x: String; } class Base2 { x: String; static s: String; } // is U extends String (S) a subtype of String (T)? Apparent type of U is String so it succeeds class Derived2 extends Base2 { // error because of the prototype's not matching, not because of the instance side x: U; } //// [apparentTypeSubtyping.js] // subtype checks use the apparent type of the target type // S is a subtype of a type T, and T is a supertype of S, if one of the following is true, where S' denotes the apparent type (section 3.8.1) of S: var __extends = (this && 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 Base = (function () { function Base() { } return Base; })(); // is String (S) a subtype of U extends String (T)? Would only be true if we used the apparent type of U (T) var Derived = (function (_super) { __extends(Derived, _super); function Derived() { _super.apply(this, arguments); } return Derived; })(Base); var Base2 = (function () { function Base2() { } return Base2; })(); // is U extends String (S) a subtype of String (T)? Apparent type of U is String so it succeeds var Derived2 = (function (_super) { __extends(Derived2, _super); function Derived2() { _super.apply(this, arguments); } return Derived2; })(Base2);