[New API] IsIterator field on DeclarationModifiers type

[CoolCoderSuper]

Background and Motivation

For quick reference the file can be found here The purpose of this api is to solve this issue in the make member static analyzer.

C# does not have the explicit Iterator api and when using the SyntaxGenerator the modifier is dropped. The type already has features that are language specific (ie IsUnsafe) so I would see no harm in supporting this as well.

This would bring the option for generators to create iterator methods closer to reality (not necessarily important).

Proposed API

namespace Microsoft.CodeAnalysis.Editing
{
     public readonly record struct DeclarationModifiers
     {
+           public bool IsIterator => (_modifiers & Modifiers.Iterator ) != 0;
     }

This would also include the corresponding WithIterator() api.

Usage Examples

Alternative Designs

Not having the API and having language specific code in the analyzer.

Risks

Possible confusion since it only exists in VB.

[CyrusNajmabadi]

Why does this need to be public? As opposed to just fixing GetModifiers to include this data internally to ensure that WithModifiers doesn't remove the modifier?

[CoolCoderSuper]

I suppose it wouldn't have to be but this would allow new generation to have the modifier applied. But maybe that doesn't matter since you would still have to deal with yield return vs Yield.

[CoolCoderSuper]

@CyrusNajmabadi just so I understand, your proposal would be the same just internal rather than public?