https://issues.dlang.org/show_bug.cgi?id=23525

          Issue ID: 23525
           Summary: Allow user-defined GC scanning for library types
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: john.michael.hall@gmail.com

From https://forum.dlang.org/post/ooraoriyrftjrpoygtnk@forum.dlang.org

Allow user-defined GC scanning for library types

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