BaseNamespaceDeclarationSyntax is derived by:
- FileScopedNamespaceDeclarationSyntax
- NamespaceDeclarationSyntax
All declarations have Externs, Members, Usings, and Name, in addition to AttributeList and Modifiers, as well as NamespaceKeyword trivia.
File-scoped namespace declarations also have a SemicolonToken trivia.
Block namespace declarations also have a CloseBraceToken, OpenBraceToken, and SemicolonToken trivia.