[jayrulez]

A closure's type is its delegate's, from the delegate's project (corlib for most), and IsTypeAccessible and IsTypeUsed checked a tuple's fields and a delegate's signature but neither for a closure: its captures were never scanned, and as a BfClosureType is no BfDelegateType it has no delegate info of its own. So a closure capturing a type of a project an executable does not reference passed as accessible, its module was marked used whenever a used module reached it, and the executable's vdata named it: the link failed on the other project's symbols.

    namespace SharedGlobals
    {
        static // in LibC, which TestsB does not reference
        {
            public static int32 LibCCaptures(LibCCaptured captured)
            {
                delegate int32() get = scope () => captured.mValue;
                return get();
            }
        }
    }

With LibA holding globals of the same namespace and TestsB calling them, TestsB failed to link on LibCCaptured.__Equals. A closure now counts as accessible and used only when its captured fields' types and its source delegate are.

Seen in a game engine where every executable that did not reference its GUI library failed to link once a second GUI library added globals to the GUI's namespace.