https://issues.dlang.org/show_bug.cgi?id=21111

          Issue ID: 21111
           Summary: One pragma(inline, true) introduction increases phobos
                    build time by 10x
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: andrei@erdani.com

I suspect it hits some pathological case in the optimizer. Fix: https://github.com/dlang/phobos/pull/7577

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