Type system incorrect on imports

[poteat]

The type system allows import A from "arcsecond", but this doesn't actually work, as the value of A is undefined in this context.

My preferred remediation would be to export the A interface entirely as a default, so that the values actually exist. An alternative remediation is to fix the type system such that the above results in a type error, forcing people to use import * as A from "arcsecond".