What would it mean to "decorate an export"?

[rbuckton]

This is a question often brought up in other issues (most recently in https://github.com/tc39/proposal-decorators/issues/69#issuecomment-409734868) that might need to be better explored. The way I see it, there are a number of specific subtopics related to this:

• If you could "decorate" any export, what would you expect to be able to do?
• How would decorating an export affect the static semantics for import/export?
• How would you apply a decorator to the following statements in a consistent and unambiguous way:
  • export * from "module";
  • export function F() {}
  • export class C {}
  • export default function() {}
  • export default class {}
  • export default expr;
  • export { x };
  • export { x as y };
• Are there runtime semantics concerns with decorating exports?
• Are there security concerns with decorating exports?