Signature Help: Prefer non-obsolete overloads

[MaStr11]

Fixes #49609

[MaStr11]

This line is copy/paste from

roslyn/src/Features/Core/Portable/LanguageServices/SymbolDisplayService/AbstractSymbolDisplayService.AbstractSymbolDescriptionBuilder.cs

Lines 248 to 250 in a30b09e

	private async Task AddDescriptionPartAsync(ISymbol symbol)
	{
	if (symbol.GetAttributes().Any(x => x.AttributeClass.MetadataName == "ObsoleteAttribute"))

That logic should be extracted (e.g. static bool IsObsolete(this ISymbol symbol) somewhere). I haven't done this, because the logic seems to be implemented way better already:

roslyn/src/Compilers/Core/Portable/Symbols/Attributes/CommonAttributeData.cs

Line 72 in a30b09e

internal static bool IsTargetEarlyAttribute(INamedTypeSymbolInternal attributeType, int attributeArgCount, AttributeDescription description)

and

roslyn/src/Compilers/Core/Portable/Symbols/Attributes/AttributeDescription.cs

Line 443 in a30b09e

internal static readonly AttributeDescription ObsoleteAttribute = new AttributeDescription("System", "ObsoleteAttribute", s_signaturesOfObsoleteAttribute);

But this logic is not accessible in this layer. Many Symbol implementations also have an ObsoleteAttributeData ObsoleteAttributeData property, but that is also internal, not part of any interface, and not accessible from here.

So I don't know what's the best way forward to avoid code duplication in this case.

[allisonchou]

Hmmm, my initial inclination is that creating an IsObsolete extension method in somewhere like ISymbolExtensions would be the best path forward. Like you mentioned, I don't think we're able to access the other logic since it's in the compiler layer.

Maybe @CyrusNajmabadi has some thoughts on this?

[CyrusNajmabadi]

yes. we should just have a single extension for this in the IDE that all these locations use.

[MaStr11]

I have found one more occurrence of that pattern and replaced it with the new extension method in 7128e78.

[CyrusNajmabadi]

tiny recommended changes.

[CyrusNajmabadi]

Thanks!!