Why do protocols have to inhabit global namespace

[ibex10]

I don't understand this: why do the protocols have to inhabit the global namespace?

Why can't we nest them inside other types?

enum World {
   protocol Foo {} // Error: Protocol 'Foo' cannot be nested inside another declaration
}

[anon9791410]

Allow nested protocol declarations

Type nesting allows some convenient and straightforward semantics that we see inside the Swift standard library such as views on String like String.CharacterView, String.UnicodeScalarView, etc. However a protocol cannot be nested in a type and gives a non-obvious error that the “Declaration is only valid at file scope.” Just as other nested types allow proper contextual scoping, a nested protocol could make a lot sense for a number of patterns. For example, there are many “Delegate” protocols th…

Nested Protocol

Is there a particular reason for not being allowed to declare a protocol nested inside another declaration? It seems reasonable to me to establish a direct relationship between a type and a protocol, when the latter has its use restricted within the scope of the former, for example.