[Issue 16322] New: Improve error message for missing module declaration

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=16322

          Issue ID: 16322
           Summary: Improve error message for missing module declaration
           Product: D
           Version: D2
          Hardware: x86
                OS: Mac OS X
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: iamthewilsonator at hotmail.com

if a file in a structed directory a/b/c/d.d has no module declaration and is
imported as `import a.b.c.d` the error message is 

module d from file a/b/c/d.d must be imported with 'import d;' 
importing as `import d;` will also fail if (very likely) a/b/c/d is not in the
import path.

Issue a warning that no module declaration is present, indicating that may be
the cause.

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