Module-owned type identity

A nominal type's declaring module is part of its identity. Two modules may both export Flag; their values remain distinct even if the variants look identical.

Use a module prefix on types, constructors, and patterns to state which declaration you mean. Bare lookup prefers the declaration in the current module.

use cli
use web

fn main() {
  println(cli.show(cli.Flag.On))
  println(web.show(web.Flag.On))
}