Add DebuggerDisplay for SearchValues

[stephentoub]

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Author:	stephentoub
Assignees:	stephentoub
Labels:	area-System.Runtime
Milestone:	-

[EgorBo]

Just a general question: why this can't be just ToString() impl?

[MihaZupan]

I'm using this in my testing, helps a ton when there are multiple generic variants.

Type implType = searchValuesInstance.GetType();
string impl = $"{implType.Name} [{string.Join(", ", implType.GenericTypeArguments.Select(t => t.Name))}]";

E.g.
SingleStringSearchValuesThreeChars`2 [ValueLength8OrLonger, CaseSensitive]

[MihaZupan]

Overriding ToString seems reasonable as well

[stephentoub]

This is effectively a collection. We don't override ToString on collections, and if we did, this wouldn't be the format chosen. The purpose of DebuggerDisplay is to raise for quick consumption the most relevant information for debugging purposes, not for runtime formatting. We should also feel free to frequently change a DebuggerDisplay rendering whereas doing so with ToString would not be desirable as code can take a dependency on it, it can be persisted in logs, test output, etc. This also needn't increase app size and can be trimmed as a debugger display.