[API Proposal]: SymbolDisplayFormat for fully-qualified metadata names and open generic types

[alrz]

Background and Motivation

The former already exists as QualifiedNameArityFormat but it's internal, useful while roundtripping names to GetTypeByMetadataName.

Currently there's no support for the latter which is useful to generate typeof expressions.

Proposed API

namespace Microsoft.CodeAnalysis;

public class SymbolDisplayFormat
{
    // eg: SomeNamespace.SomeType`1
    public static readonly SymbolDisplayFormat FullyQualifiedMetadataFormat;

    // eg: global::SomeNamespace.SomeType<>
    public static readonly SymbolDisplayFormat FullyQualifiedOpenGenericFormat;
}

Alternatively, both could be exposed as members of SymbolDisplayGenericsOptions.

[333fred]

To proeed with this, I think we'd need to be very crisp about what this format flag does, and where. Does it follow a specification in some manner? What is its behavior when combined with other flags? This needs to be more fleshed out before we can review.

[alrz]

To proeed with this, I think we'd need to be very crisp about what this format flag does, and where. Does it follow a specification in some manner? What is its behavior when combined with other flags? This needs to be more fleshed out before we can review.

I think the metadata name could be an extension on type symbol that internally uses a formatting flag.

Open generics actually makes sense in source, so it could be an explicit flag?