Clarify nested scope for type parameters from outer scope

[BillWagner]

See #681 (comment)

Changes necessary for default interface members may require changing the wording in §7.7.1 (Scopes / General). In the following, the outer T is hidden by the inner T.

interface IOuter<out T>
{
    interface IInner<T>
    {
        class C { }
    }
}

§7.7.1 currently says:

The scope of a name is the region of program text within which it is possible to refer to the entity declared by the name without qualification of the name. Scopes can be nested, and an inner scope may redeclare the meaning of a name from an outer scope. (This does not, however, remove the restriction imposed by §7.3 that within a nested block it is not possible to declare a local variable or local constant with the same name as a local variable or local constant in an enclosing block.) The name from the outer scope is then said to be hidden in the region of program text covered by the inner scope, and access to the outer name is only possible by qualifying the name.

Within the definition of interface IInner<T> , it is not possible to refer to the T type parameter of IOuter. According to this wording then, the definition of class C is not in the scope of the outer T.

Alternatively, we could include "including any nested scopes" to the restriction here.

[jskeet]

(Self-assigned for the sake of triage/investigation, not actually fixing the issue...)

[jskeet]

I think this is okay already. I think C is still within the scope of the outer T, it's just that the outer T is hidden as described in the rest of the paragraph.

I suspect we would deem C to be in the scope of the outer T everywhere in the spec, including other restrictions etc.

Proposal: either close the issue, or propose a change to 7.7.1 to clarify that a name is still "in scope" for all other purposes in the spec, even if it's hidden by declaration in a nested scope.