68 lines
2.6 KiB
TypeScript
68 lines
2.6 KiB
TypeScript
//// [apparentTypeSubtyping.ts]
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// subtype checks use the apparent type of the target type
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// 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:
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class Base<U extends String> {
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x: U;
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}
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// is String (S) a subtype of U extends String (T)? Would only be true if we used the apparent type of U (T)
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class Derived<U> extends Base<string> { // error
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x: String;
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}
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class Base2 {
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x: String;
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static s: String;
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}
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// is U extends String (S) a subtype of String (T)? Apparent type of U is String so it succeeds
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class Derived2<U extends String> extends Base2 { // error because of the prototype's not matching, not because of the instance side
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x: U;
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}
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//// [apparentTypeSubtyping.js]
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// subtype checks use the apparent type of the target type
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// 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:
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var __extends = (this && this.__extends) || (function () {
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var extendStatics = function (d, b) {
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extendStatics = Object.setPrototypeOf ||
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({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
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function (d, b) { for (var p in b) if (Object.prototype.hasOwnProperty.call(b, p)) d[p] = b[p]; };
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return extendStatics(d, b);
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};
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return function (d, b) {
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if (typeof b !== "function" && b !== null)
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throw new TypeError("Class extends value " + String(b) + " is not a constructor or null");
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extendStatics(d, b);
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function __() { this.constructor = d; }
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d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
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};
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})();
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var Base = /** @class */ (function () {
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function Base() {
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}
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return Base;
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}());
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// is String (S) a subtype of U extends String (T)? Would only be true if we used the apparent type of U (T)
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var Derived = /** @class */ (function (_super) {
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__extends(Derived, _super);
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function Derived() {
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return _super !== null && _super.apply(this, arguments) || this;
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}
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return Derived;
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}(Base));
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var Base2 = /** @class */ (function () {
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function Base2() {
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}
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return Base2;
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}());
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// is U extends String (S) a subtype of String (T)? Apparent type of U is String so it succeeds
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var Derived2 = /** @class */ (function (_super) {
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__extends(Derived2, _super);
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function Derived2() {
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return _super !== null && _super.apply(this, arguments) || this;
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}
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return Derived2;
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}(Base2));
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