[Issue 23850] Differentiate between a module that is in binary vs outside of binary when including -I

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23850

--- Comment #2 from Richard Cattermole <alphaglosined at gmail.com> ---
Am I right to understand the core problem you are describing @kinke is
duplicate symbols?

If so, I am not sure how any exporting attributes could fix this scenario when
you are duplicatiing including object files in your program. You're going to
have hidden state that is duplicated which puts your program into an unknown
state as you use it.

But that does lead to a question if a build manager detects an include +
external include matching, should it error rather than pick? Because now I'm
thinking that yes it should error because things are not going to do what you
want.

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