[Issue 15086] import doesn't verify module declaration

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=15086

--- Comment #10 from Jonathan Marler <johnnymarler at gmail.com> ---
> I think at the least we can do a vastly better job at issuing error messages.

I'm limiting focus to this issue alone. Do you have an idea on a way to improve
the error message for this case?

CURRENT BEHAVIOR
----------------------------
dmd -c foo.d bar.d
Error: module baz from file bar.d must be imported with 'import baz;'

PROPOSED BEHAVIOR
----------------------------
dmd -c foo.d bar.d
Error: module baz from file bar.d must be imported with 'import baz;' or must
be compiled separately

--