Importing a second module enables FQN sidestepping selective import

[dlangBugzillaToGithub]

Simen Kjaeraas reported this on 2019-09-19T07:38:52Z

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

Description

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.