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digitalmars.D.bugs - [Issue 21731] New: SumType should provide convenient access to the


          Issue ID: 21731
           Summary: SumType should provide convenient access to the type
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: phobos
          Assignee: nobody puremagic.com
          Reporter: snarwin+bugzilla gmail.com

This feature was requested on the D forums [1].

It is possible to compute the type index in user code, but the implementation
is a bit verbose, and easy to get wrong:

size_t typeIndex(Val)(Val val)
    if (isSumType!Val)
    alias QualifiedTypes = CopyTypeQualifiers!(Val, Val.Types);
    return val.match!(v => staticIndexOf!(typeof(v), QualifiedTypes));

For both convenience and correctness, it would be better if this functionality
were included in the `sumtype` module.

[1] https://forum.dlang.org/post/ouqgmoxzlcyrfqxsrtnm forum.dlang.org

Mar 18 2021