Changed IDE0059 codefix title in pattern matching

[DoctorKrolic]

Fixes: #40002

[CyrusNajmabadi]

@DoctorKrolic Answered on Discord. Thanks! :)

[DoctorKrolic]

@CyrusNajmabadi please review

[CyrusNajmabadi]

Thanks!

[DoctorKrolic]

@CyrusNajmabadi I checked failing integration tests and found out, that IsUnusedLocalDiagnostic will be reported for all unused local nodes, e.g.:

class Program
{
  public static void Main()
  {
    var x = new Program();
  }
}

x will have IsUnusedLocalDiagnostic tag, but codefix will produce this code:

class Program
{
  public static void Main()
  {
    var _ = new Program();
  }
}

So the decision of whether should node be removed or changed to discard is fully implemented in codefixe's code. This method replaces all declaration patterns with type declarations:

roslyn/src/Analyzers/CSharp/CodeFixes/RemoveUnusedParametersAndValues/CSharpRemoveUnusedValuesCodeFixProvider.cs

Lines 79 to 93 in afe689a

	protected override SyntaxNode TryUpdateParentOfUpdatedNode(SyntaxNode parent, SyntaxNode newNameNode, SyntaxEditor editor, ISyntaxFacts syntaxFacts)
	{
	if (newNameNode.IsKind(SyntaxKind.DiscardDesignation)
	&& parent.IsKind(SyntaxKind.DeclarationPattern, out DeclarationPatternSyntax declarationPattern)
	&& parent.SyntaxTree.Options.LanguageVersion() >= LanguageVersion.CSharp9)
	{
	var trailingTrivia = declarationPattern.Type.GetTrailingTrivia()
	.AddRange(newNameNode.GetLeadingTrivia())
	.AddRange(newNameNode.GetTrailingTrivia());
	return SyntaxFactory.TypePattern(declarationPattern.Type).WithTrailingTrivia(trailingTrivia);
	}
	return null;
	}

So in cases like

var a = "str";
if (a is object obj)
{
}

declaration pattern object obj will be changed to just type declaration object

Considering this fact, I reverted logic of PR back to just checking for declaration pattern when deciding what codefix title to show

[DoctorKrolic]

@CyrusNajmabadi PTAL

[CyrusNajmabadi]

Thanks :)