error TS5055: Cannot write file 'b.js' because it would overwrite input file.
  Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
b.js(3,25): error TS8026: Expected A<T> type arguments; provide these with an '@extends' tag.
b.js(9,27): error TS8011: Type arguments can only be used in TypeScript files.
b.js(15,25): error TS8026: Expected A<T> type arguments; provide these with an '@extends' tag.
b.js(15,27): error TS8011: Type arguments can only be used in TypeScript files.


!!! error TS5055: Cannot write file 'b.js' because it would overwrite input file.
!!! error TS5055:   Adding a tsconfig.json file will help organize projects that contain both TypeScript and JavaScript files. Learn more at https://aka.ms/tsconfig.
==== a.ts (0 errors) ====
    export class A<T> {}
    
==== b.js (4 errors) ====
    import { A } from './a.js';
    
    export class B1 extends A {
                            ~
!!! error TS8026: Expected A<T> type arguments; provide these with an '@extends' tag.
        constructor() {
            super();
        }
    }
    
    export class B2 extends A<string> {
                              ~~~~~~
!!! error TS8011: Type arguments can only be used in TypeScript files.
        constructor() {
            super();
        }
    }
    
    export class B3 extends A<string, string> {
                            ~~~~~~~~~~~~~~~~~
!!! error TS8026: Expected A<T> type arguments; provide these with an '@extends' tag.
                              ~~~~~~~~~~~~~~
!!! error TS8011: Type arguments can only be used in TypeScript files.
        constructor() {
            super();
        }
    }