[Proposal]: Add private and namespace accessibility modifiers for top-level types.

[CyrusNajmabadi]

private and namespace accessibility modifiers for top-level types

• Proposed
• Prototype: Not Started
• Implementation: Not Started
• Specification: Not Started

• Discussion: [Proposal]: Add `private` and `namespace` accessibility modifiers for top-level types. #8654

Summary

[summary]: Enable the private modifier to be used for top level types in C#. The semantics of this would differ from internal in that while internal means "this assembly and any assemblies with IVT to this", private would mean "this assembly only". This is already the meaning for nested types, but is not available for top level types.

Similarly, enable the namespace modifier to be used for types in c#. The semantics of this are that these types are only accessible within that namespace only (not including sub-namespaces).

Design meetings

• https://github.com/dotnet/csharplang/blob/main/meetings/2023/LDM-2023-10-09.md#add-private-and-namespace-accessibility-modifiers-for-top-level-types