Microsoft/TypeScript
Ver no GitHubMixed es5/es2015 code with mixin classes causes runtime errors
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#17.088 aberto em 11 de jul. de 2017
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Description
TypeScript Version: 2.4.1 (but likely anything since 2.2)
When utilising code targeted at ES5 mixed with code targeted at ES6 causes a runtime error when using mixin classes. The real world use case was using a library that was targeted at ES5 for distribution compatibility reasons while downstream code is being targeted at ES2017 because of running in a known limited environment.
Code
Tagged.ts
// @target: es5
export interface Constructor<T> {
new(...args: any[]): T;
prototype: T;
}
export default function Tagged<T extends Constructor<{}>>(Base: T) {
return class extends Base {
_tag = '';
}
}
TaggedExample.ts
// @target: es2015
import Tagged from './Tagged';
class Example {
log() {
console.log('Hello World!');
}
}
const TaggedExample = Tagged(Example);
const taggedExample = new TaggedExample(); // Uncaught TypeError: Class constructor Example cannot be invoked without 'new'
Expected behavior:
No run-time errors.
Actual behavior:
A runtime error of Uncaught TypeError: Class constructor Example cannot be invoked without 'new'.