Describe the problem you are trying to solve

Incremental source generators are sometimes designed in a non-cache-friendly way. This happens when pipeline contains types that are not equatable across different compilations. These types can be ISymbols, or Compilations. Maybe also SyntaxNode? Not sure.

Describe suggestions on how to achieve the rule

The analyzer will look for incremental generator pipelines that are not cache-friendly, and issue a diagnostic.

More detailed, the analyzer will look for Register[Implementation]SourceOutput<T> invocations where T violates incrementality. Violation is defined as follows:

• Type T doesn't implement IEquatable<T> (this includes Compilation)
• Type T is ISymbol.
• Type T isn't ImmutableArray<T>
• Type T is a tuple where one of the tuple elements violates incrementality.
• Type T is a user-defined model where one of the members violates incrementality.

Alternatively, and more strongly, we can detect any part of the pipeline that violates incrementality, not only Register[Implementation]SourceOutput. This should exclude the root context.CompilationProvider, etc.

Additional context

I have seen this a lot, and in the dotnet organization. e.g, dotnet/runtime#76119 and https://github.com/dotnet/winforms/blob/117451b053c2fbda2f9caf9e1ef280f412b5aad1/src/System.Windows.Forms.Analyzers.CSharp/src/System/Windows/Forms/Generators/ApplicationConfigurationGenerator.cs#L74-L81