[oconnor663]

I think the idea is that `foo::something()` without a module declaration either implies the existence of `foo.rs`, or fails to compile. I'd agree that it would be bad if creating `foo.rs` changed the behavior of code that was previously doing something else (other than breaking the build).

What would happen, I think, is that adding a `mod foo { ... }` definition would change the behavior of code that previously implicitly referenced a `foo.rs` file. But that seems less crazy to me, since you've got a change in one file affecting something else in that same file. Or it might make sense for that to be a "conflicting module definitions" error.