[Issue 20229] New: Importing a second module enables FQN sidestepping selective import

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20229

          Issue ID: 20229
           Summary: Importing a second module enables FQN sidestepping
                    selective import
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: simen.kjaras at gmail.com

unittest {
    import std.complex : complex;
    static assert(!__traits(compiles, { alias a = std.complex.abs; }));
}
unittest {
    import std.complex : complex;
    import std.internal.test.uda; // module with no imports
    static assert(__traits(compiles, { alias a = std.complex.abs; }));
}

In the first block above, we can't refer to std.complex.abs, as it's not
imported by the selective import statement. In the second block however, the
presence of a second, non-selective, import statement makes std.complex.abs
accessible again.

Note that the module selected has no imports, and it's thus not a case of
referring to imports in that imported module.

Note also that the name of the second module is important - it needs to be in
the same package as the first imported module. I tested with a module called
`bar`, and the static assert correctly triggered, but renaming the module to
std.bar (still an empty file) made it compile again.

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