14.5.4, "Using static directives": Example needed

[RexJaeschke]

At the very end of this subclause we have the following:

A using_static_directive only imports members and types declared directly in the given type, not members and types declared in base classes.

TODO: Example

Ambiguities between multiple using_namespace_directives and using_static_directives are discussed in §14.5.3.

We need someone to provide the example or to argue against doing so.

[jskeet]

Quick example - there may be better ones...

This compiles:

using System.Text;
using static System.Text.Encoding;

public class Test
{
    static void Main()
    {
        Encoding utf8 = UTF8; // Encoding.UTF8 is imported automatically
    }
}

But this doesn't:

using System.Text;
using static System.Text.ASCIIEncoding;

public class Test
{
    static void Main()
    {
        Encoding utf8 = UTF8; // UTF8 isn't declared directly in ASCIIEncoding
    }
}

[jskeet]

Eric-inspired note: We can't work out the motivation behind this rule. It would be nice to note it if we can dig it up. @MadsTorgersen, any help here?

[jskeet]

(We suspect that understanding the rule may help come up with a better example, so assigned to Mads.)

[BillWagner]

Per Jon's comment that mentioned @MadsTorgersen

The rule in question:

"A using_static_directive only imports members and types declared directly in the given type, not members and types declared in base classes."

I suspect the reason for this rule is that without it, any using static would import the static methods declared in System.Object: Equals(Object, Object) and ReferenceEquals(Object, Object). With any deeper hierarchy, that would be confusing.

[BillWagner]

Discussed in June 30th meeting: That decision is to encourage developers to use the canonical names of types being importing in a using static rather than rely on the effects of inheritance.

A downside is that it means moving a static member to a base class should be interpreted as a breaking change, because the using static directives would be incorrect.

[BillWagner]

Added in c5ce449