Incorrect errors on duplicate export { x as y }

[Rich-Harris]

The new duplicate export checking is great and will allow us to remove some code from Rollup. However, it looks like it's throwing errors wrongly in cases like these:

acorn.parse(`
  export { x as y } from './y.js';
  export { x as z } from './z.js';
`, { sourceType: 'module' });
// SyntaxError: Duplicate export 'x' (3:11)

acorn.parse(`
  export { default as y } from './y.js';
  export default 42;
`, { sourceType: 'module' });
// SyntaxError: Duplicate export 'default' (1:51)

(Also, the location in that second error message looks suspicious?) I can try and make a PR if I get time this weekend. Thanks!

[marijnh]

I've fixed this and released 4.0.1 with the fix.