https://issues.dlang.org/show_bug.cgi?id=20818

          Issue ID: 20818
           Summary: Support const, scope, etc. attributes for variadic
                    parameters
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: bugzilla@digitalmars.com

Currently, they are accepted but ignored.

A start:

https://github.com/dlang/dmd/pull/11125

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