Treat [NullString]::Value as the string type when resolving methods

[daxian-dbw]

PR Summary

Fix #18072
Treat [NullString]::Value as the string type when resolving methods.

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Label      : Small
Size       : +42 -17
Percentile : 23.6%

Total files changed: 3

Change summary by file extension:
.cs : +22 -17
.ps1 : +20 -0

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[SeeminglyScience]

LGTM!

[iSazonov]

LGTM with one notice.

[iSazonov]

Is it really hot path code? If so we could think about more tier-compilation-friendly methods:

        internal static Type GetObjectTypeAfterDebase(object obj)
        {
            obj = PSObject.Base(obj);

            return obj == NullString.Value ? typeof(string) : obj?.GetType();
    }

        internal static Type GetObjectTypeWithoutDebase(object obj) => 
obj == NullString.Value ? typeof(string) : obj?.GetType();

[dkaszews]

I think I know C# pretty well but never considered it from performance side. In C++, this function would be almost guaranteed to be inlined and the if discarded or made unconditional. Is C#'s optimizer really not capable of it? Do you have some optimization guidelines I could read, e.g. when to use [AggressivelyInline] I saw in some WriteToConsole overloads?

[iSazonov]

For reading https://devblogs.microsoft.com/dotnet/performance_improvements_in_net_7/

[daxian-dbw]

This seems to be a micro-optimization that we should avoid, as I don't think the difference is measurable.