https://issues.dlang.org/show_bug.cgi?id=17214

          Issue ID: 17214
           Summary: std.array.Appender has an unnecessary indirection
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: phobos
          Assignee: nobody@puremagic.com
          Reporter: jack@jackstouffer.com

The internal variables are stored in a Data struct which is then allocated on the GC and stored as a pointer in the struct. While this reduces the size of Appender, this indirection is unnecessary and also results in extra GC memory being allocated than needed.

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